Slugging Percentage/Power Factor in Baseball
The Importance (or lack thereof) of Defense
A word of warning: This inning will be an exercise in remembering baseball abbreviations, but if you hang in there, things will make sense. But we need to start at the very beginning, with the obvious question: What is defense?
As one example of interest, in baseball it is conventional to divide the essential skills of the game into three categories: batting, pitching, and defense. The three are generally held to be, broadly speaking, of comparable significance. In the now--semi-mythical Golden Age of baseball, a championship team was expected to be generously endowed with all three attributes; in this dilute modern era of over-expansion, teams performance specialize.
When the option is for strong pitching, the inevitable concomitant is tight defense. The managerial (and front office) preference is then for the player with the silken fielding, even if his hitting isn't so hot; conversely, a player with a good bat will be snooted if his fielding clanks and wheezes a bit. Even teams that go the other route, relying on their slugging to overcome mediocre pitching, will occasionally reverse that pattern for one or two of the key defensive positions (typically shortstop or catcher), especially in the American League, where there is no "automatic out" at #9; a big-hitting team will often feel that it can afford to carry a very weak hitter if he is a defensive gem, say a Mark Belanger or a Roger Metzger. (I well remember a bubble-gum card of Metzger, then sporting a near-.200 career average, which said, "Forget his bat! Just watch his glove!" Roger, incidentally, was a fine lefty platoon hitter, but few realized it then.)
In sum, the traditional wisdom of baseball is that defensive skills are exceedingly important, and that the teams that lacks them will leak runs like a sieve. Pitchers on such teams shudder and reach for the antacid when they're called to the mound. Well, let's see if we can find some less-than-mystical way of finding out just how bad it really is (or isn't). To paraphrase Lord Kelvin, if you can't put it in numbers, you don't know much about it.
From Eric Walker's The Sinister First Baseman, "You Could Look It Up"
The question we are exploring is this: How important is defense to a major league ball club, and what could be more important to a team than great defense?
To the extent that conventional measurements are made of fielding, they are of minimal significance. I will assume that you are familiar with the definitions of Putouts, Assists, and Errors, and know that their sum is called Total Chances. Putouts and Assists don't require much discussion, but a few thoughts on Errors may be in order.
First the scoring concept of `Error' does not even pretend to address the question of whether or not a given fielder has the inherent ability to get to a particular ball, although a casual reading of the scoring rules might seem to indicate otherwise. (In theory, you don't even have to touch a ball to get an Error, but unless it goes right though your legs, we're pretty much talking about muffing a ball you touched.) Second, while there is a rising tide of sentiment of the `team error' concept to cover those ridiculous `hits' where two or three fields Alphonse-and-Gaston an easy pop-up that any one of them could have handled blindfolded, it hasn't happened yet; they're still called Errors. Third, it seems ludicrous to give an Error to a fielder whose perfect throw (usually from the outfield) hits a flaw on the field, or even the runner himself, before being caught. There's more, but in short, the `big E' is obviously a somewhat subjective concept of dubious utility.
So then, if we can't trust errors (and I don't know many baseball people who do), we must have another way to measure how good (or bad) a team is defensively. Walker gives us the `traditional' baseball methods of measuring fielding performance.
(Total Chances minus errors, divided by Total Chances) A perfect FA is 1.000; major league average runs in the high .900s.
- Fielding Average (FA)
But this figure is meaningless. I could play Major League Baseball for twenty years and field 1.000 lifetime: all I have to do is never get close to a ball. No touch, no error; 1.000 FA. Naturally, I wouldn't last twenty years, or even twenty minutes, fielding that way, but I choose a comically extreme example. In cold fact, there is a large number of slow, limited-range fielders who are, in any realistic sense, terrible, but who sport very high FA's.
The more TCs a man has, the more balls he's getting to. This is an improvement, but not a big one. You can only compare a player with others at the same position; at that, they may be playing behind very different types of pitchers, and thus have significantly more or fewer balls hit at all near them.
- Total Chances (TC)
Some fans go solely by Errors. This is the worst approach of all. Many fine fielders regularly extend themselves (figuratively and literally) for balls others wouldn't dream of getting to; if your shortstop gets to 50 balls that would have gone right through another infield and successfully handles 30 of them for outs, your team is 30 outs ahead, but the shortstop in question is 20 Errors `ahead'.
- Errors
So what do we do?
Applying these conventional approaches to team fielding is rarely tried, as the results would be meaningless...Overall team Errors are sometimes cited, but we have already seen how foolish that is likely to be. Are we then lost and helpless? Hardly. All we need do is apply a little common sense to basic concepts.
The object of a defense is to put out all batters that come to the plate. However; one of the defenders, the pitcher, is a vital part of this process, and needs to be measured apart from the rest. So how do we separate pitching from fielding?
Walker begins by eliminating all batters that have no effect on the defense's fielding: strikeouts, walks, hit by pitches, and homeruns. (He acknowledges that there is a small percentage of HRs that might have been caught, but the number is so small it's negligible.) He then takes the total number of opposing batters that a team faces in a season (the "BFP" figure of pitching statistics) and subtracts out K, BB, HBP, and HR.
What we have left is the total of batters who, in one way or another, put the ball into play. I will call this number "BIP" (balls in play); it is the total number of opportunities the fielders actually had to make outs. If we can now determine how many outs they did make, we can get some idea of their success percentage.
This is straightforward; we need only take the total of all Putouts recording in the fielding stats, and subtract Strikeouts. This result I dub "Fielders Outs" or FO. To get Fielding Efficiency (FE) as a percentage, we merely divide FO by BIP.
Walker then calculates a chart of all major league teams' using "Fielding Efficiency" (his new, created stat (FE)) and compares it to "Conventional FA" (the `traditional baseball' measure of defense) from 1979-1980. The teams don't matter anymore, but to illustrate his point, I'll give you the lines of the best fielding team (according to the new FE stat), the worst, and the A's, who were right at the league average at the time.
Best - Baltimore = FE .7745, FA .982
Average - Oakland = FE .7530, FA .975
Worst - Chicago (NL) = FE .7393, FA .974
Walker makes two initial observations. The first one is that there is a huge advantage for teams who play the majority of their defense on Astroturf (the vast majority of the Astroturf teams were in the top seven in fielding). The second observation is the simple fact that if you organize the calculated FE's for each team from highest to lowest (or best to worst), they are not in the same order as the old FA calculations would have been.
Obviously, our new "FE" is tracking something substantially different. Equally obviously, it is a more sensitive gauge: our top FE is about 1.05 times the bottom one, whereas the top FA isn't even 1.01 times the lowest (a very narrow range).
Further observation and reflection will reveal a number of additional indicators that the FE is a useful and valid overall indicator of team fielding quality; it is, after all, measuring the only really meaningful criterion-how many of those you could have put out that you did put out. But now all we have is the tool; we have yet to work with it.
What we really want to know is the significance of these FE differences: what do they tell us about winning and losing?
Walker then performs a series of calculations which correlate runs scored to Fielding Efficiency (FE). He takes the Chicago Cubs (the worst defenders in the league at the time) and improves their FE to the major league average. Based on their "BIP" (Balls in Play) figure, if their defense went from the worst in the league to the league average, they would allow 65 or 66 fewer baserunners per season. In 1982 (and I can only imagine that it's similar today, although I did not do the calculations), 12.26 percent of all BIP runners eventually score. So out of the Cubs' 65 or 66 baserunners allowed, somewhere around eight runs would score overall.
By coincidence, the difference in runs scored or allowed per season which usually corresponds to one game more won or lost is 8 runs for the NL, 9 for the AL); for example, a .500 National League team which normally both scores and allows 650 runs over a season will win 82 instead of 81, if it instead scores 658 or allows 642 (if it does both, it will win 83, on average). In sum, improving the worst-fielding team in the major leagues to a completely average team's level would most likely gain it only one extra victory per season.
Let's think about that for a minute. One game is all you gain by revamping an entire team's defense from the worst in the league to simply average. So what happens if your goal is to be the best fielding team in the majors?
We may also look at the other extreme, the top. The incredibly talented Orioles, if reduced to utter normality would give up an extra 12 runs (give or take 1 or 2); this would cause an absolute maximum win-loss swing of two games, and far more likely only--again--one game. And if we descend even so little as one step down from the top, to the Astros, it is not even clear that there would be any won-lost difference (we're talking four runs or so).
As the most extreme example imaginable, suppose the Cubs acquired the Orioles' fielding abilities: what would they gain? Just twenty fewer runs yielded, give or take 3; that's a swing of three games at most, and perhaps only two. Remember, too, this is imagining an improvement from the very worst to the very best, in one jump!
Please note: Improving your club from the worst fielding team to the best fielding team in the Major Leagues will gain you at most three games a season. This somewhat subtly suggests the idea that games are not won by the marginal differences in defensive abilities.
This all demonstrates, among other things, how selective our memories are. We remember well the brilliant plays our shortstop has made, the incredible, eye-popping leaps and dives; we also remember the shocking misplays, the slow rollers through the legs, the routine throws that sailed, and so on. What we forget are the literally thousands of routine plays our fielders make every season, the little F7's and G63's that mainly fill our scorecards. We forget, in short, how much baseball (like the national debt) is absolutely and irrevocably foreordained, and how very little the marginal differences in player skills can actually influence things. "It's a game of inches"; how incredibly true that is. In virtually every baseball stat, we need two and most often three significant digits for the number to mean anything. Imagine if we rounded off batting averages to just two places!
This makes sense. It does. Keep in mind that the worst defensive player still is a major league baseball player, i.e. he is good, and according to the numbers, there is just not that big of a difference over the course of a season between a good major league player and a great one; by the time they make the major leagues, the routine plays will be made by any major leaguer, and the spectacular plays, although they look great on Sports Center, just do not happen often enough to make much of a difference to a team over the course of a season. There is just not enough opportunity in baseball to separate most major league players by defensive ability; how teams are set apart from each other is by offensive capabilities and, of course, pitching. Not that defense is not important, we've all seen spectacular defense save games, and awful defense lose games, but the numbers don't lie. It simply does not happen enough to make much of a difference in a team's overall win/loss record.For a player's overall value to a team, defense is nowhere near as important as offense.
And as for the playoffs, although we all long for that gold glove defender at key positions during the big games, what we have to keep in mind is that our team most likely would not be IN the playoffs without the offense that those players provide. Meet Manny Ramirez. He is not going to win any OF Gold Gloves; however, it doesn't matter as much as traditional baseball says it should. He is an offensive powerhouse, and that matters more. This was never more evident as it was in Game 1 of the World Series last year. Manny attempted to play left field. Likewise, David Ortiz played first base. But both of them hit. Which created offense. Which gave the RedSox runs. And that was an extreme example; Manny is not usually that costly in left. We instinctively know this rings true, even if we didn't before know how to prove it.
If there's a specific lesson in all this, and I believe there is, it is that fielding is dramatically overvalued. Most--the vast majority, in fact--of all plays will either be executed by virtually any man at the position or will be unmakeable by anyone. Pitching is commonly said to be (variously) 90 percent of the game, or 75 percent of the game, or some such. It is not; defense overall is exactly 50 percent of the game, period. The swing in staff earned runs from best team to worst averages almost exactly 162 per season, which probably represents about 20 games' worth; the swing from best to worst in fielding is, as we have seen, perhaps 2 games' worth. Thus, pitching accounts for 20 out of 22 games, or around 90 percent of overall defense; clearly, then, it is only 45 percent of the total game.
Let's pretend for a moment that Derek Jeter is a MUCH MUCH better defensive shortstop than Alex Rodriguez. (Yes, yes, the same Jeter that won a Gold Glove solely by one single play diving into the stands, because that's all people remember about his defense, and please note, I said pretend!) If Derek Jeter, the best shortstop of ALL TIME is in the game, he's the best defensive man you could possibly have at the position, and that should count for a lot, right? Wrong. Walker is saying that if your team is smart, you'd take either Tejada or Rodriguez over Jeter (assuming you don't have all three) simply due to their offensive numbers; that any player brought up to the Major League level as a shortstop is at least competent enough to make the vast majority of all plays, and the cost from the ones he didn't, CAN, in fact, be made up by his offensive numbers. This also makes sense.
Furthermore, pitching is as valuable as we think. A twenty game swing decided solely by a pitching staff is as important as it sounds, and accounts for the vast majority of a team's defense. Yet, by traditional baseball wisdom, a team's fielding ability behind its pitchers is often considered every bit as important as the pitchers themselves; yet as we consider the numbers, we find that this is certainly not the case.
If I could talk to Eric Walker, I would like to have him expound more on catcher defense, although I'm inclined to use his same measurement for catchers as well. From what baseball has taught us, Mike Piazza is a pretty good example. He's consistently ranked very low on the 'I Can Catch' scale, yet he's a coveted prize because of his awesome offensive power numbers. Would you sacrifice defense for those kinds of numbers? The answer is a resounding `yes'! According to calculations by both Eric Walker and Bill James (and I'm sure countless others), a great offensive player can add two more wins by themselves to a team's total over a season. One single player! It seems to be simply icing on the cake when the catcher is an offensive powerhouse and can catch and throw.
A player's fielding can and should be a part of his overall evaluation, but the smaller part. Only when two players are quite closely matched in offensive capabilities should their defense be closely regarded. One key offensive player alone can strengthen a team enough to add two more games to their annual games-won total; yet completely and utterly revamping that entire team on a defensive basis will probably not yield more than a single extra game, if that. You figure it out. End of lesson; class dismissed.Slugging Percentage/Power Factor in Baseball
As we learned in the 4th Inning, slugging percentage is a popular measure of a hitter's power, and is calculated by total bases divided by at bats.
TB = (1b) + (2 x 2B) + (3 x 3B) + (4 x HR)
Walks are not included in the above calculation.
However, walks are a huge part of a players' OBP calulation, so if you combine OBP with SLG, you have a true measure of how good of a hitter a player really is.
From Eric Walker's The Sinister First Baseman, "The Babe and the Asterisk":
Assuredly, noticeable difference exist between home-run figures from those times and the corresponding modern figures. But such differences, while they are indicative, are trends, and by no means specific enough to settle any discussions, at least not any in which the disagreements are vehement. Fortunately, we can use those statistics more precisely if we just think about it a bit.
The fact is that home run totals by themselves are not an accurate measure of power in hitting. Consider two players, A and B (how original), both of whom come to the plate some 700 times in a given season, and both of whom hit 15 home runs. Are they equally powerful hitters? Not at all. If A walks 10 percent of the time and bats .260, he has 15 homeruns in 164 hits; meanwhile, the free-swinging B walks 5 percent of the time and bats .301, so his 15 homeruns are distributed over 200 hits. As to power, pure power, we clearly sense that A has more of it than B.
We might thus think to try home runs per ht as a measure of power; after all, a man's power is not diminished by strikeouts or walks. This is not a bad measure, but we can do a little better if we remember that there are hits other than home runs that also reflect a solidly hit baseball. Certain parks, by their physical nature, discourage home runs, either by dead air or by deep or high fences, or by all of these. In such parks, the incidence of doubles and triples will consequently be higher than average, as many balls that would clear a fence elsewhere will instead fall in for extra-base hits. Conversely, in cheap home run parks, one would expect somewhat fewer doubles and triples than normal.
The drift of this argument, as you perceive, is that total bases per hit is a somewhat more sensitive and revealing measure, tending as it does to average out home-park differences. Let us call this figure, the ratio of total bases to hits (or of slugging average to batting average, same thing), "The Power Factor," or just PF. With it, we presume to measure the relative average amounts of energy that a batter imparts to the baseball on those occasions when he succeeds in hitting it at all.
From what I can tell in this chapter, this is the precursor to the now-commonly used Slugging Percentage. I'm guessing in that 1982, homeruns were the primary means to measure a hitter's power, so Walker is arguing against measuring a player's homeruns and more for his slugging percentage, which is as it should be. He calls his measurement the "Power Factor" and it is built on a scale from 1.00-2.00. Of course, the names come immediately to mind: Barry Bonds, Albert Pujols, David Ortiz, Manny Ramirez, Sammy Sosa, Jason Giambi, Jason Kendall (for contrast, of course!). When I first read this chapter, I had to pull up stats to plug into the following equations, just to see how accurate he was, and what he was really measuring.
Before we plunge headlong into use of this new toy, we might take a further moment to get some feel for it. One thing we would expect is that if this thing measures what we think, if should, for any given batter, be at least moderately consistent from season to season. We would also expect a significant range of values, one that essentially corresponds to our intuitive feelings about players. To investigate these points, one could tabulate dozens of players' results for a number of seasons, and the reader is free to so amuse himself if he chooses. For those not inclined to lengthy research and calculation, some approximate feeling for contemporary power factors may be gained from the listing below.Walker then graphs the last 100 years of baseball, using power factor. He notices that the 1.5 average holds constant through the years, despite all the changes that have occurred in the game.
A Power Factor of 2 is very rarely seen, even on a single-season basis; on a career basis, there will be at most half a dozen active players at 2 or over, and usually fewer (Mike Schmidt and Gorman Thomas are just barely over 2.0 on a career basis). The overall average for major-league batters nowadays is around 1.5.
PF Type of Power
1.00 to 1.15 So lightweight as to almost never be seen.
1.15 to 1.25 Pure spray singles hitter; few doubles, no homers
1.25 to 1.35 Typical non-power hitter; some doubles, a few homers
1.35 to 1.45 Modest power; usually only a few homers, but lots of doubles
1.45 to 1.55 Medium power; typically 10+ homers, plus many doubles
1.55 to 1.65 Good power; perhaps 20 homers a year
1.65 to 1.75 Very good power
1.75 and over Excellent power; a real slugger
As an aside, we may note that a couple of major changes in the game, changes that were supposed to vastly alter offense, had little or no effect on PF. The first was the expanded strike zone of the later `60's (1963-1968); the second is the DH Rule (in effect in the American League since 1973). This makes perfect sense, since the Power Factor measures what a batter achieves when he hits the ball. Making the ball harder to hit will have little effect on this measure. Similarly, replacing a pitcher with a DH will yield more hits, more home runs, and more runs scored, but little if any change in the ratio of home runs to hits or total bases to hits.Walker then compares Ruth to Maris, in an attempt to find out who was the heavier slugger. On a side note, on a trip to Baltimore, not only did I have a chance to see Camden Yards, but Babe's birthplace as well. There was something about seeing the exact house where he was born, the streets where he played, that just brings any good baseball fan to tears. Special moment there.
Note:For those inclined to play with some numbers from current players, but lacking full statistical data, here are some fairly workable rule-of-thumb approximations that relate hits (H), home runs (HR), and Power Factor (PF):
So what do we know now about Ruth vs. Maris? We know that in 1927, Ruth's PF of 2.172 was 157 percent of the major-league average for the year, while Maris' 1961 PF of 2.302, while higher in an absolute sense, was but 149 percent of the average for that year. In other words, if Ruth had gotten the same number of hits in 1927, but using a 1961 baseball, he most likely would have slugged 77 home runs that year! (I spare you the in-between calculations; they are simply based on PF ratios.
No contemporary player comes near Ruth's adjusted equivalent Power Factor of 2.4 or thereabouts from 1927. He far exceeded his contemporaries, and the degree by which he did so is also mind-boggling. In 1973, Hank Aaron achieved 40 round-trippers in only 118 hits; yet he exceeded the general PF of his times by only 45 percent (only!), compared to Ruth's 57 percent (and Maris' 49 percent). .Incredible performances all, but there was only one Sultan of Swat.
(1) PF = ( 3 x HR) + 1.227
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H
(2) HR = H x (PF - 1.227)
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3
Current Examples:
Barry Bonds - PF from 2001 = 2.6
Albert Pujols - PF career = 1.84
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