Scouting Science: Does height matter for MLB pitchers?

It has long been held true by many baseball traditionalists that bigger players are better players, especially pitchers. Players have grown over the years - as have Americans in general - and pitchers have stayed taller than hitters. But how much does height actually affect a pitcher's value? Instead of just accepting an old baseball truism, I decided to put it to the test. My instruments: inches for height and VORP (value over replacement player) for value.

Looking at the entire list of pitchers who got at least one major-league out in the 2007 season – excluding guys like Jeff Cirillo and Josh Wilson as position players who made their way to the rubber during blow outs – there are 694 pitchers whose average height is 74.46 inches. They compiled an average VORP of 7.76. That makes the Jon Lieber (VORP 7.7, height 74 inches) the most average pitcher in 2007.

Take a look at the average 2007 VORP for all MLB pitchers grouped by height:

Good enough, right? Taller pitchers are better than shorter ones.

While the bar graph shows a fairly strong positive correlation between VORP and height, it is somewhat misleading. The height boundaries were chosen to try and make each group as equal as possible, however the extreme right and left of the graph represent the tails of a height bell curve. The group of 2007 MLB pitchers who are 6-foot-7 or taller (79+ inches) consists of just 22 hurlers and the 5-foot-10 and under group (<70) only has 13 members.

C.C. Sabathia and Aaron Harang (both 6-foot-7) throw off the distribution by themselves as their combined performances represent something of an outlier in the data. Pedro Feliciano (5-foot-10) sets the high water mark for the <70 inches group with his 15.4 VORP while the rest of the group leaves a lot to be desired – Byung-hyun Kim’s -14.3 VORP almost negates Feliciano’s single handedly (Kim is 5-foot-9).

The correlation for all 2007 pitchers’ VORP and height is just 0.086, which straddles the line between very small positive correlation and statistically insignificant.

But maybe that number is being dragged down by the Byung-hyun Kims of the world, and the Sabathias and Chris Youngs represent a new paradigm in pitching excellence?...turns out, not so much.

Breaking the data set down into deciles, the pitchers in the top 10% by VORP are taller than any other group and have a stronger correlation between value and height (0.113). Here's a scatter plot of the top decile:

The line of best fit is pointing up, though only slightly. Chris Young is the data point at the very top (45.8 VORP, 82 inches tall) and Ian Snell is at the bottom (42.8 VORP, 71 inches tall). All in all the 69 best pitchers give hope to the bigger is better theory that many scouts, general managers, coaches, and fans have assumed true for generations.

However both the seventh and ninth deciles have slightly stronger correlations between value and height (0.125 and 0.115 respectively) and the second decile (or the top 11-20% of pitchers in 2007) actually has a very slightly negative correlation, -0.023.

Conclusions

As you step back from the numbers you see that height has very little to do with VORP for major league pitchers.

Some traditionalists will suggest that the biggest bonus a relatively tall pitcher can give to an organization is the durability his large frame allows for – though the correlation I calculated between height and innings pitched was only 0.07...and the correlation between height and strikeout rate was an even smaller 0.05.

My research suggests that height has very little to do with a pitcher's value, although there are more positive outliers among the very tall than the very short.

Potential Problems

I wonder about there being a selection bias with short pitchers, in that only the very, very best ever get a shot while taller pitchers are given chances more freely.

The converse may also be true, in that a compensation effect could be in play here. Shorter pitchers – especially righties – could know that they will be given less of a shot and therefore work harder...a positive baseball version of a Napoleon complex.

Height is not a perfect measure of size. It is not exact, it is not static, and I sometimes question the validity of the numbers I came across. How many guys were given “roster bonuses”?

Methodology

I used the greatness of Baseball-Reference.com to find the heights, with official team pages being my backup. I tried to use one site as often as possible to keep the numbers consistent.

Baseball Prospectus’ freely available statistics section was used to find the VORP for all pitchers.

Pitchers who were traded during the season have different entries for each team they played for in 2007. I tried my best to consolidate all the numbers of pitchers who threw for multiple teams – like Kim who pitched for Arizona, Colorado, and Florida in 2007 – but it is possible that one or two players are counted twice. This shouldn't effect the data in a significant way, however.

As stated earlier, the <70 inch group had 13 members. The 70-72 group had 117. The 73-74 group had 222. The 75-76 group had 222 as well. The 77-78 group had 90. And again the 79+ group had 22.

I have the numbers from this study in an Excel spreadsheet that I will share with anyone who would like to see it.

Lincoln can be reached at lhamilton@dentonoutlaws.com.