A recent study shone a light on a fact that is in plain view: There is more Left-handed representation in Baseball at the Pitcher position than the general population. The disparity is not insignificant. Depending on the resource cited lefties account for about 10% of the population plus or minus a point or two. At the major league level, however, the percentage is almost three times that. The study cites the value at 27.5%. But, a check of the player data base for 2018 yields a figure close to 30%. What’s going on?
First of all, the study was looking for differences in the bio-mechanics of Left Handed Pitchers versus Right Handed Pitchers. (LHP/RHP) The study then concluded that the only data points that trended were the following: “Landing position of the stride foot, trunk separation at foot contact, maximum shoulder external rotation and trunk forward tilt at ball release were all significantly greater in right-handed pitchers.” Curiously the conclusion reached was that the differences were of, “…minimal practical significance.” This is at odds with the results of a different study in 2015 which was discussed here on Talknats during December of that year in a piece titled, “The Future of Pitching.” In that study the most reliable predictor of velocity was the ground force exerted upon the stride leg during delivery. Stride-length and velocity are linearly related. What the more-recent study did, probably unwittingly, was lay out a perfect case that RHPs should have a higher velocity, on average, than LHPs. For that we have data.
Sort starting pitchers any which way you’d like. Whether it’s Earned Run Average, Hits Allowed, or Wins Above Replacement the lists look very similar. Nick Pollack at Pitcher List has his list of Top 100 starting pitchers. One advantage is that it includes players like Stephen Strasburg who didn’t reach an innings trigger to be included on certain official statistics lists. Of his top 50 starters 16 are Left-handed (34%). The average 4-seam fastball velocity is 92.7 mph. The top velocity belongs to James Paxton at 95.51 mph. The comparison to RHP velocities is not kind. Paxton doesn’t crack the top-ten of RHP velocities. On average, these 34 RHPs came in at 94.2 mph. The median values are almost identical to the averages. The data shows that Lefty fastballs are slower than their Right-handed colleagues.
This raises all manner of questions. The most obvious is perhaps the hardest to answer; why? It may be rooted in the fact there are so many LHPs in the game. If you were to start a youth league the odds are that the kids showing up would mimic the handedness proportions of the general population. There would be 9 to 11 kids throwing Southpaw. At each level as they progress the Lefties would find a wider gate to get through to advance than their Right-handed counterparts. In this mythical youth league, if an impossibly high 10-percent of the group made it through to the Bigs, consider some odds. With 10 pitchers making it through the gauntlet, 3 are going to be LHP. The odds of one of the original 9-11 kids making it are 33%. For the Righties, only 7 of about 90 will make it. The odds of any one kid making it through are a considerably lower at about 9%. The competition for the Right-handers is tougher at every stage of the process. The crop that emerges on the other side should be better as a group. In the modern game the currency of pitching is the fastball. It should not be a surprise that we see the difference manifest itself there.
The second question is also difficult to answer; if LHPs throw the fastball slower then why are they representatively effective? The LHP population in the various top 40/50/100 lists is consistently around 30%. Any numbers of them are top-shelf performers including Chris Sale, Clayton Kershaw, and the Nats’ shiny new acquisition Patrick Corbin. Sale has the fastest 4-seamer of the three. But, there are 15 RHPs who are faster. Adding mud to the water is that most batters are Right-handed. The proportion of 58% is considerably lower than the general population. Add another 12% who Switch-hit and the odds are that a Southpaw will face the unfavorable Right-handed matchup 7 out of 10 times. With all that’s going against them why do they do so well? The answer has to lie somewhere in a combination of breaking ball effectiveness and delivery angle. There are estimates out there of “Perceived Velocity” where the velocity appears faster to the batter than the radar gun due to aspects of the delivery. Tampa sensation Blake Snell is one of the leaders on most of these lists.
What we know about fastballs is that there is a steep shelf in effectiveness between 93 and 94 mph. At 90-93 mph the batting average against is .278. Raise that a few mph and the batting average drops to .251. Keep in mind that the average speed for the LHPs was 92.7 mph. In aggregate MLB is batting .266 against fastballs. Conversely, the average against breaking balls is .211. The saving grace for Southpaws has traditionally been that big old, “Uncle Charlie” curve. Baseball, as a whole may be following suit. The percentage of fastballs thrown this year fell from 60.7% to 55.4%.
What stands out about this skewed distribution of handedness among Pitchers is how it is isolated to just them. Only 15% of the top 100 hitters both bat and throw Left-handed. That is close enough to the distribution within the general population to call it within the margin of error. The 12% that hit from both sides of the plate all throw with the right arm. Baseball may lag golf in bio-metric studies by a wide margin. But, the game figured out something golf has only stumbled on by accident: A player with a dominant right hand has an advantage hitting the ball with the dominant arm leading. Some 30 of the top 100 hitters throw Right and bat Left exclusively. Tour-level golf has such a paucity of lefties that the sight of one is an event. Phil Mickelson has been an exception for a long time. Other than golf, he is exclusively Right-handed. The arrangement provides such an advantage that it is a small miracle it has not spread.
If you have MLB pitching aspirations for your toddler, you might want to consider your first purchase to that end being a Left-handed mitt. It might be the biggest single advantage he could have.