The MLB Draft: Is Drafting High School LHPs A Bad Idea?

Anecdotally, left-handed pitchers are different from right-handed pitchers. Other than the fact they use a different arm to throw the baseball, I mean. Left-handers seem to often be of the "crafty" variety, using deception, a multitude of different pitches and good command to their advantage. Anecdotally, then, it seems like teams would pick up their lefties - their Mark Buehrles and their Ted Lillys - quite late in the draft, as it's much harder to scout the "crafty" types than measuring the velocity of a power pitchers. And it seems I'm not alone in thinking this, quoting Minor League Ball's Matt Garrioch:

The biggest difference between left handed pitchers and righties is velocity. Left handers typically throw slower than righties and are typically more control oriented pitchers. CC Sabathia is the exception here, but Jarrod Washburn, Doug Davis and Randy Wolf are the more typical left handed pitchers to succeed.

But then I went and researched where the successful starters of today have been drafted, and the results support the theory only partially. Note that I used ERA- to judge if the pitchers were successful, using 101 (tiny bit below average) as the minimum. High school draftees made up 14 of 29 successful left-handers (48%), and 23 of 52 (44%) of successful right-handers.

The results only support the idea that teams get their left-handed former college pitchers from later rounds, but since they get their successful high-school lefties from the 1st rounds more often, lefties are not, on average, picked up lower in the draft than righties. Most interesting about these results are the low amount of successful high school lefties picked up early in the draft. Is there usually a run on left-handed prep pitchers early? And do they have higher or lower success rates than right-handed prep pitchers taken in the same rounds?

If one lists all high school pitchers taken in the 2004-2008 draft with 50th pick or lower, we get 31 HS RHPs, and 14 HS LHPs. So it seems that any early run on left-handed pitchers did not occur in those years, and in fact the opposite seems true, as the percentage of lefties taken here (31%) is quite low. The success rate for the lefties was also quite low (21%), but the three that didn't bust - Gio Gonzalez, Clayton Kershaw and Madison Bumgarner - went on to be stars. I don't think it makes sense to really compare the success ratio with a sample size this small, but the rate of drafting very good players (which is what the Jays will be aiming for) seems to be fine.

Kiley McDaniel recently tweeted that he thought the Jays would pick either Reese McGuire (HS C) or Trey Ball (HS LHP), depending on who the Pirates pass on. Will they shoot for the stars with a left-handed prep pitcher? We'll see. Tomorrow is draft day!