The A's are way ahead with respect to biomechanics, and none of their starters bothers with the slide step. A's starters also have great balance & posture across the board, FWIW.

I hear ya, Bill, though data collection is extremely difficult - one would need to break down each pitcher's individual slide-step context and measure the HR rates from there. It would require classifying every pitcher in the league as a slide stepper or non, and not everyone employs the slide step to the same degree - the crafty vets that mix in the slide step selectively would require pitch-by-pitch tracking from the stretch. The effect is also more pronounced on the first few pitches from the stretch, before a pitcher can make adjustments, which further complicates the target sample. There are also confounding variables when parsing pitchFX data that make it tough to isolate an effect, such as the findings by our own Max Marchi regarding fastball velocity that increases in critical situations: http://www.baseballprospectus.com/article.php?articleid=17352

I have mentioned some specific examples in Raising Aces, and in fact I showed a visual comparison of Stephen Strasburg's new slide step here: http://www.baseballprospectus.com/article.php?articleid=17146

I encourage you to look for this phenomenon when watching games, rather than take my word for it. I think that you will notice that many pitchers lack command from the stretch, particularly those who employ the slide step, and that the command issues are more often manifested as under-rotation.

I will say that, in general, if pitchers were equally effective with a slide step, then the obvious solution would be to pitch that way all the time. Why harness two timing patterns when one will suffice? Coaches know that they are sacrificing something to achieve a quicker release, and the degree of impact is very much player-dependent, with wide variance across the league.

The .1-.2 seconds comes via research that we did for "Arm Action," in addition to measurements that we made regularly at the National Pitching Association. Keep in mind that the .1-.2 seconds is compared to a regular stretch delivery (not the windup).

I agree that there is more to be mined here, however I feel that the philosophical exercise underscores the "insanity" - why would we create any obstacle to pitch execution in order to thwart such a rare occurrence, particularly when the methods employed only have a marginal impact on the end-goal?

There are many examples that can be observed in the numbers. For example, Brandon Morrow was a mess with the slide step for the last two years, and the impact to his line is clear. I would watch games where he just could not get the ball down due to constantly early rotation, which helps to explain why he was so "unlucky" to get only one GIDP in 2011. But he has addressed the issue in 2012 and is finally finding his release point with the slide step, which is a factor underlying his improved numbers. In fact, if you watch the mlb.tv feed from the game on June 6, the announcers discuss these exact improvements (2nd inning, after Pierzynski's single). Someone studying the numbers might look at the 2012 to '11 disparity and scream "noise" and "small sample size," but watching the game with a mechanical bent will often reveal why the numbers are what they are.

To be fair, there are other pitchers who will struggle from the stretch with a more standard leg kick - just watch any Tim Linececum start from the last month to see what I mean.

Yes. Yes. Yes.

In general, generating strong early momentum is a good thing, and it often results in a shorter time into foot strike. This will increase the kinetic energy in the system, though the torque will be more reliant on timing and sequencing. Both momentum and torque contribute to velocity, but torque plays a much bigger role.