George_Foreman wrote:i basically agree with what Magney said, but at the same time, it's tough to quantify how distracted a pitcher by certian players with higher propensities to run.
for instance, and interesting study would be to check, say, the rays's #2 hitter's BA when crawford is on first vs. when he is not on first. at least some of that difference could be attributable to his abilty to steal 2nd, and thus should be factored in to the bennefits of his steals. so, IMO, you can probably get away with a success rate slightly blow 75 and still have a net gain provided the speedster has enough of a reputation to throw pitchers off their rhythme.
Actually, there have been studies on the impact of stealers on hitters and it's opposite to what you suppose. Hitters have POORER performance when there's a stealer on base than when he's not. One guess as to why that is so is that the base runner is just as or even more distracting to the hitter, since that runner leads to those annoying pick-off throws that disturb your rhythm and timing and also is moving in your field of vision as you try to hit, disturbing your concentration.
I'll see if the studies I've seen are online and try to post links.