July 18, 2001

Doctoring The Numbers

The Burroughs Hypothesis

by Rany Jazayerli

Sean 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 long-awaited power had still not arrived (he's hitting .352 in Triple-A, but with only five home runs in 236 at-bats.) Referring to the fact that he bats left-handed but throws right-handed, 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 lefty-lefty.

Burroughs also pointed out fellow Futures Game teammate Adam Dunn, also a left-handed hitter but a right-handed 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 right-field 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 lefty-swinging, righty-throwing 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 1920--when home-run power became relevant--through 1993, a total of 318 players have batted 250 or more times in a major-league 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 left-handed. Of those 118, 43 throw left-handed (we'll call them L-L), and 75 throw right-handed (L-R).

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

>.200         2           12          14
.160-.200    10            5          15
.120-.160    13           14          27
.080-.120    14           30          44
<.080         4           14          18

This breakdown defies any obvious trend. On one hand, L-R hitters were responsible for 12 of the 14 seasons with the most left-handed power before age 22. The only two L-L hitters with an isolated power above .200 were Griffey (1991) and Darryl Strawberry (1983). Among the L-R 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, L-L hitters show more power than L-R hitters. Twenty-five of the 43 L-L hitters (58%) had an ISP of .120 or higher. Just 31 of 75 L-R hitters (41%) did the same. Overall, the 43 L-L hitters under age 22 had an ISP of .136. The 75 L-R hitters had an ISP of .131, a five-point difference.

Is that significant? Maybe not. Left-handed-throwing infielders (except for first basemen) are as rare as a funny skit involving Tim Meadows, owing to the fact that a left-hander would have to pivot awkwardly when throws to first base. Left-handed-throwing catchers are also essentially non-existent, although I have yet to hear a good reason why.

So it would stand to reason that L-L hitters would have more power than L-R hitters anyway, because L-L position players can only play first base or the outfield. If we look at a control group by comparing L-L hitters vs. L-R hitters at, say, age 30, we find that L-L hitters have a combined ISP seven points higher (.145) than L-R hitters (.138). That disparity is two points higher than the difference between young L-L and L-R hitters, although the difference between the two numbers is probably not statistically significant.

To put it in simple terms--in case Allard Baird is reading this Web site for the first time--among left-handed hitters who make it to the major leagues at an early age, those who throw left-handed appear no more likely to exhibit precocious power than those who throw right-handed.

But that isn't exactly the point Burroughs was trying to make. His claim is, in essence, if two young left-handed hitters both show only modest power, the one who throws right-handed is more likely to develop power in the future than the one that throws left-handed.

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

<.080         4           14          18

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, L-L and L-R, have virtually identical power totals; the L-L hitters have an ISP of .059, the L-R hitters .061. If we fast-forward and look at how the players perform five years later, do the L-R hitters hit for more power than the L-L hitters do?

Only two of the four L-L hitters were still playing regularly five years later, and they combined for an ISP of .119. Nine of the 14 L-R 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

<.080       4  .059       2  .119        14  .061       9  .095    -26

"Difference" refers to how much L-R hitters improved relative to L-L hitters. In this case, L-R hitters saw their ISP increase by 34 points five years later, compared to the 60-point increase enjoyed by L-L hitters. Since the L-R hitters improved by 26 points less than the L-L 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   Diff

>.200       2  .224       2  .301        12  .246      10  .198   -125
.160-.200  10  .185       8  .170         5  .168       5  .160     +7
.120-.160  13  .140      11  .175        14  .136      10  .170     -1
.080-.120  14  .099      10  .111        30  .098      24  .139    +29
<.080          .059       2  .119        14  .061       9  .095    -26

The top row is skewed by the incredibly small sample size of the L-L 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 L-L or the L-R hitters. However, that 29-point advantage enjoyed by the L-R hitters in the next-to-bottom 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

.120-.160  45  .141      37  .154        6   .137      45  .155     +5
.080-.120  39  .098      22  .113        60  .103      38  .120     +2
<.080      16  .060      10  .108        39  .062      22  .107     -3

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 L-L middle infielders and catchers means that, overall, L-L hitters have more power than L-R 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 L-L 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

.120-.160  18  .144      15  .162        23  .139      15  .167    +10
.080-.120  21  .100      19  .121        23  .104      19  .145    +20
<.080       7  .068       4  .115        12  .066       9  .107     -6

There might--stress might--some evidence here to back up Burroughs' claim. The L-R 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 L-R hitters in the other two groups are fairly sizable. If we combine all three rows together, giving us a total sample size of 38 L-L and 43 L-R seasons in the follow-up group, L-R 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 L-R hitters is real: the advantage appears to fade as the players age. The 11-point edge for L-R hitters includes all outfielders 22 and under. If we look solely at outfielders 21 and under, the advantage is actually 13 points; for 22-year-olds, it slips to seven points. Among 23-year-old outfielders, there doesn't appear to be any advantage at all; in fact, L-L hitters actually fare two points better than L-R 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 minor-league players would feature enough young players, but trying to compare hitters at various minor-league levels might only muddy an issue that is murky enough as it is.

And even if the L-R 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 L-R player like Burroughs (who is still just 20 years old) to pick up an extra 13 points of slugging average relative to his L-L 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 25-homer 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.

Rany Jazayerli is an author of Baseball Prospectus. 
Click here to see Rany's other articles. You can contact Rany by clicking here