Does Size Matter? (Part 1)

In a recent column for Heater Magazine, I wrote that I expect Jeff Francoeur to improve because he’s a big guy, and has a hitter’s frame. As much as I dislike scout-speak, this is a statement I feel comfortable making, mainly because it’s backed up by the numbers.

Big hitters generally hit better. It’s not hard to imagine why that would be the case; bigger guys can generate more power, and there’s also a strong case of selection bias that forces them to be good hitters. Big guys are generally slower, due to all that extra bulk, so they’re not going to have much defensive value. To make it to the big leagues, then, they better be able to hit.

The selection bias works the other way as well. Smaller ballplayers are generally quicker and can man tough fielding positions; thus, their hitting skill is not required to be as great. It works both ways, and in the end, the big guys tend to be the ones making noise with their bats. Just how much noise? Let’s find out!

First, the details of my study: I looked at all post-World War II player seasons. That means that if a player’s career spanned both before and after the war, I included only his post-war years. I then divided the players into four separate groups: The big guys, the beanpoles, the pudgy ones, and the little guys. The requirements for each group were, in order, 6’3”+ and over 205 pounds; 6’3” and no more than 170 pounds; 5’10” or less and more than 205 pounds; and 5’10” or under and 170 pounds or less.

Here’s a chart detailing each group’s performance per 650 plate appearances, or about a full season:

Group  	       AB    H   2B  3B  HR  SB  CS  BB   SO  HBP  GIDP  SH  SF    BA   OBP   SLG   GPA
Tall, Heavy   576  153   29   3  25   5   3  64  113    5    15   2   5  .266  .342  .454  .267
Tall, Light   604  151   21   7   8  22  16  37  115    4    14   6   5  .250  .296  .350  .221
Short, Heavy  599  177   30   4  19   8   5  42   96    4    16   2   5  .296  .344  .452  .268
Short, Light  586  153   24   5   7  18   8  56   71    4    11   9   4  .261  .328  .355  .236

Okay, there’s a lot of information here, so let’s go through it carefully. First of all, we see that batting averages have little to do with anything. The pudgy guys have a much higher batting average than everyone else, but that’s because well over half of that sample is made up by Kirby Puckett. Remove him, and the short and heavy group bats .257, well within the range of everyone else.

Power correlates well with weight. The big guys are obviously the most powerful, with 25 home runs per year and a .454 slugging average. The pudgy players are just as powerful without Puckett (21 home runs per 650 plate appearances), as with him (19 a year).

Strikeouts tend to go up as height goes up, which makes sense because the taller you are, the bigger your strike zone. It should be noted that when I remove Puckett, the pudgy group’s strikeout rate goes way up to 124, but I think this is more a sample size fluke than real effect.

Speed is an interesting factor. Obviously, less weight means more speed; that’s not surprising. What is surprising is that the lanky players seem to be perceived as much faster than they actually are. While they do steal four more bases a year, they’re also caught on the base paths twice as much. They ground into double plays at about the same rate as the two heavy groups, and more often than the little guys, indicating that they’re not much faster than the average player. Perhaps they make more outs on-base as well.

Patience doesn’t really correlate with size so much. The most patient hitters are the big guys and the little guys, and that isn’t even a bit surprising. The big guys walk a lot because they’re good hitters, and (a) good hitters are partially good because they’re patient, and (b) pitchers tend to pitch around good hitters. That first point may seem irrelevant since it would seem that the point I’m trying to make is that big hitters are good because they’re big, but as I mentioned earlier, that’s not necessarily true due to selection bias. It may just be that the only big guys called up to the major leagues are the good hitters, because if you can’t hit—and being tall and heavy, you probably aren’t exactly a nimble fielder—you have little value to a major league baseball team. The little guys walk a lot because many of them are batting near the top of the lineup due to their speed and sac bunting skills, and of course, walks are extremely valuable for a table-setter.

The disproportionate (tall, skinny; short, fat) players don’t walk so much because they aren’t very good hitters.

This fact is attested to by that last column, which displays the Gross Production Average (GPA) of each group. GPA measures a player’s overall performance on a scale similar to batting average. In the period we’re looking at, the average GPA has been just about .250. The tall and heavy players are well above average at .267. The short and heavy players look great with Kirby Puckett (.268), but a little below average without him (.245). The small players are well below average at .236, but they likely make up for that with good glove work at tough positions (we’ll look into that in a bit). The lanky players are the worst, with a miserable .221 GPA.

Why might that be? One theory is that lanky players are simply guys that never filled out. Many players are drafted with the assumption that they can add muscle to their frames and will get bigger and stronger as they develop. Some simply do not. Maybe a subset of those players is nevertheless promoted, and still fails to get bigger. Whatever the case, it seems clear that lanky players are not a good bet to succeed.

Okay, now let’s go back to my theory about the little guys being good fielders. Let’s look at the same group of players, only this time let’s break down where they played in the field. For this particular exercise, we only care about the little guys and the big guys (also, there are some serious sample size problems when it comes to playing in the field for the other two groups). The following chart shows the playing-time breakdown by position for each group:

Group	        Catcher  First Base   Second Base  Third Base  Shortstop  Outfield
Tall, Heavy	9%	 37%	      0%	   6%	       3%	  46%
Short, Light	2%	 1%	      29%	   11%	       29%	  28%

A few things are clearly apparent. The big guys play almost exclusively at first base and outfield (and in the outfield, they’re mostly likely playing in right or left, rather than the more defensively-valuable center), while the majority of the little guys (or more accurately, the majority of the games the little guys play) are in the middle infield. 97% of their games are either at second, third, shortstop, or in the outfield, and I would imagine that a large part of the small outfielders are center fielders. Clearly, the little guys are manning the tougher positions, and in all likelihood, that makes up for their lack of offensive production.

The little guys may be as valuable as their larger counterparts, but they derive much of their value from a different source. Meanwhile, the rarer lanky or pudgy player should continue to be an uncommon occurrence, as they are clearly worse hitters and probably cannot make up for that in fielding prowess due to having less speed (which correlates well with fielding ability) than the small guys.

A Hardball Times Update
Goodbye for now.

This much is clear. But how does this all impact Francoeur? He’s already big; is his size an indicator of future success? Next week, we’ll examine whether or not the knowledge we’ve acquired today about the correlation between player size and performance helps us project a player’s future production, or whether any effect size has on a player’s future numbers is already accounted for by his regular batting line.

References & Resources
I couldn’t have done any of this without the always-fabulous Lahman Database. However, the database does not quite contain full height and weight information, so the players for whom a height or weight was not listed were removed. I also removed Eddie Gaedel, the 3’7″, 65 pound player who was brought in for one plate appearance by the 1951 St. Louis Browns, and walked.

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