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July 18, 2001 Doctoring The NumbersThe Burroughs HypothesisSean Burroughs is not content with being one of the best hitting prospects in all of baseball. He also wants to make his mark in the field of sabermetrics.In an interview with David Schoenfield, ESPN.com editor and one of the most underrated members of the sabermetric revolution, Burroughs gave a novel answer as to why his longawaited power had still not arrived (he's hitting .352 in TripleA, but with only five home runs in 236 atbats.) Referring to the fact that he bats lefthanded but throws righthanded, Burroughs said:
I think it takes a little more time for our power to develop. Our dominant hand is our right hand, but you need power from both hands when you hit. Guys like [Ken] Griffey and [Barry] Bonds, they're leftylefty. Burroughs also pointed out fellow Futures Game teammate Adam Dunn, also a lefthanded hitter but a righthanded thrower, who after hitting "just" 27 home runs over the past two years, already has hit 30 this season. Is Burroughs on to something? It's true that Ken Griffey Jr., a lefty all the way around, was dropping bombs in the rightfield bleachers from the time he was a teenager. And as Schoenfield writes, "it's an interesting concept, especially since Burroughs is often compared to George Brett, a leftyswinging, rightythrowing third baseman who hit only 20 home runs his first three years in the majors." The anecdotes piqued our interest, but to test Burroughs's hypothesis, anecdotes won't suffice: we need hard data. Fortunately, we have it. >From 1920when homerun power became relevantthrough 1993, a total of 318 players have batted 250 or more times in a majorleague season at age 21 or younger. (The same player can be counted more than once; Griffey, for example, qualifies three times.) Of those 318, only 118 batted exclusively lefthanded. Of those 118, 43 throw lefthanded (we'll call them LL), and 75 throw righthanded (LR). Using Isolated Power (slugging average minus batting average) as a measure of power, we can divide players into five different cells: less than .080, .080.120, .120.160, .160.200, and greater than .200. So we can break these 118 players down this way:
Power Throws L Throws R Total This breakdown defies any obvious trend. On one hand, LR hitters were responsible for 12 of the 14 seasons with the most lefthanded power before age 22. The only two LL hitters with an isolated power above .200 were Griffey (1991) and Darryl Strawberry (1983). Among the LR hitters, Mel Ott did it three times by himself, Ted Williams and Eddie Mathews twice each. But the rest of the chart indicates that, on average, LL hitters show more power than LR hitters. Twentyfive of the 43 LL hitters (58%) had an ISP of .120 or higher. Just 31 of 75 LR hitters (41%) did the same. Overall, the 43 LL hitters under age 22 had an ISP of .136. The 75 LR hitters had an ISP of .131, a fivepoint difference. Is that significant? Maybe not. Lefthandedthrowing infielders (except for first basemen) are as rare as a funny skit involving Tim Meadows, owing to the fact that a lefthander would have to pivot awkwardly when throws to first base. Lefthandedthrowing catchers are also essentially nonexistent, although I have yet to hear a good reason why. So it would stand to reason that LL hitters would have more power than LR hitters anyway, because LL position players can only play first base or the outfield. If we look at a control group by comparing LL hitters vs. LR hitters at, say, age 30, we find that LL hitters have a combined ISP seven points higher (.145) than LR hitters (.138). That disparity is two points higher than the difference between young LL and LR hitters, although the difference between the two numbers is probably not statistically significant. To put it in simple termsin case Allard Baird is reading this Web site for the first timeamong lefthanded hitters who make it to the major leagues at an early age, those who throw lefthanded appear no more likely to exhibit precocious power than those who throw righthanded. But that isn't exactly the point Burroughs was trying to make. His claim is, in essence, if two young lefthanded hitters both show only modest power, the one who throws righthanded is more likely to develop power in the future than the one that throws lefthanded. Let's get back to the chart above. In particular, let's focus just on the bottom row, which contain the players with the least power:
Power Throws L Throws R Total A total of 18 players under the age of 22 have had an isolated power of under .080. At this point in time, the two groups of hitters, LL and LR, have virtually identical power totals; the LL hitters have an ISP of .059, the LR hitters .061. If we fastforward and look at how the players perform five years later, do the LR hitters hit for more power than the LL hitters do? Only two of the four LL hitters were still playing regularly five years later, and they combined for an ISP of .119. Nine of the 14 LR hitters got 250 PA's, and their combined ISP was .095. Summarizing these findings in yet another chart:
Bats L, Throws L Bats L, Throws R Power Year 0 ISP Year 5 ISP Year 0 ISP Year 5 ISP Diff "Difference" refers to how much LR hitters improved relative to LL hitters. In this case, LR hitters saw their ISP increase by 34 points five years later, compared to the 60point increase enjoyed by LL hitters. Since the LR hitters improved by 26 points less than the LL hitters, they earn a "Difference" of 26. That's a very small sample, so let's do the same with each of the rows in the original chart:
Bats L, Throws L Bats L, Throws R Power Year 0 ISP Year 5 ISP Year 0 ISP Year 5 ISP DiffThe top row is skewed by the incredibly small sample size of the LL hitters, as Griffey is a future Hall of Famer and Strawberry looked like one for the first seven years of his career. Overall, there does not appear to be an obvious advantage for either the LL or the LR hitters. However, that 29point advantage enjoyed by the LR hitters in the nexttobottom row looks intriguing, especially since the sample size is the largest of all the rows. Now we'll look at the same chart, but change the criteria to look at slightly older hitters, guys who were 22 or 23 years old in their original season. Those players are still young enough to develop power as they age, and looking at older players provides us a much larger sample size to examine the issue. In addition, we'll eliminate the top two rows entirely, because those players have already shown they can hit for power, so they really aren't germane to the question at hand.
Bats L, Throws L Bats L, Throws R Power Year 0 ISP Year 5 ISP Year 0 ISP Year 5 ISP Diff The increased sample sizes have helped to smooth out the data, and what the data shows is that there's no real difference between the two groups. We could tweak the study in many other ways, lowering the PA requirement, looking three years ahead instead of five years, whatever. I'll agree to spare you the tedium of looking at more lists if you'll agree to trust me when I tell you that none of them show any significant difference between the two groups. There's one other factor we should consider, though. We've already established that the lack of LL middle infielders and catchers means that, overall, LL hitters have more power than LR hitters. It has also been shown (by Bill James, in the 1987 Baseball Abstract) that, presumably owing to the physical demands of their positions, second basemen and catchers tend to develop less than players at other positions. Since there are no LL hitters at either position, is it possible that if we match players from each group with players at the same position, that a difference between the two groups will finally emerge? Only one way to find out. The following chart consists only of players who were 22 and younger, and who were primarily outfielders during their original season (defined as 50 or more games played in the outfield):
Bats L, Throws L Bats L, Throws R Power Year 0 ISP Year 5 ISP Year 0 ISP Year 5 ISP Diff There mightstress mightsome evidence here to back up Burroughs' claim. The LR hitters do not fare well in the bottom row, but the sample size is by far the smallest of the three groups, and the advantages shown by the LR hitters in the other two groups are fairly sizable. If we combine all three rows together, giving us a total sample size of 38 LL and 43 LR seasons in the followup group, LR hitters have an overall advantage of 11 points of isolated power. I imagine there's a way to determine whether a difference this large, in a sample this large, is statistically significant or not. Unfortunately, I neglected to take that particular class in college, so I'm forced to use inference to determine whether the difference is real or not. And there is at least one additional reason to believe that the advantage enjoyed by young LR hitters is real: the advantage appears to fade as the players age. The 11point edge for LR hitters includes all outfielders 22 and under. If we look solely at outfielders 21 and under, the advantage is actually 13 points; for 22yearolds, it slips to seven points. Among 23yearold outfielders, there doesn't appear to be any advantage at all; in fact, LL hitters actually fare two points better than LR hitters. Nevertheless, I'm not willing to hang my hat on Burroughs's statement just yet. To reach a firm conclusion would require a study of hundreds of hitters, and there simply isn't enough data available, at least not in the major leagues. A study including minorleague players would feature enough young players, but trying to compare hitters at various minorleague levels might only muddy an issue that is murky enough as it is. And even if the LR advantage is real in statistical terms, is it significant in baseball terms? Suppose we use the most generous evidence in the study and project a young LR player like Burroughs (who is still just 20 years old) to pick up an extra 13 points of slugging average relative to his LL counterpart, say someone like Josh Hamilton, over the course of the next five years. Thirteen points of slugging average comes out to about seven total bases over the course of a season, the equivalent of converting three singles into a double and a pair of home runs. That's not trivial, but neither is it large enough to change the outlook of a young player one way or the other. Or to put it another way: if Burroughs develops the 25homer power that everyone expects from him, there will be no reason to think he wouldn't have developed his home run swing had he thrown with his left hand. Rany Jazayerli is an author of Baseball Prospectus. You can contact him by clicking here.
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