I've mentioned this in VEB Monitor already, but the conversation on ground-ball pitchers and injury (and attrition, more generally) that Rob Neyer has been spontaneously facilitating on Baseball Nation is fascinating, especially if you're a St. Louis Cardinals fan who's received the ground-ball gospel from Dave Duncan and his successors for the last 15 years. Bill James and Craig Wright, two of the original sabermetric heroes, have offered some theories as to why ground-ball pitchers don't seem to last as long, at their best, as their fly-ball counterparts.
Here's how Wright responded to Neyer on the subject (there's more at the link):
First, let me lay to rest any notion that sinkerballers are not working hard because they tend not to throw as fast as the average pitcher. A sinkerballer is in fact working quite hard to get the speed of his sinker up to a workable speed. [...] I believe the big issue with sinkerballers is that most continue to have as good or even better sinking action when their arm is a little tired. That doesn't happen with a normal fastball, which tends to lose effectiveness when the shoulder crosses the line of fatigue.
This is a twist worthy of Agatha Christie, if it's accurate: The same endearing fact broadcasters love trotting out about sinkerballers, that they're best once their arms are tired, is exactly what causes so many of them to flame out after a few great years. Why would their manager pull them when they're pitching better than usual?
Of course there are other possible explanations; many sinkerballers have low strikeout rates, and low strikeout rates leave them with little cushion as their peripherals decline. But pitchers like Brandon Webb, whose careers end more catastrophically, don't fit that description. Sinkerballers are stereotyped as workhorses because they seem so much less fussy than their smoke-throwing counterparts, but it could just be that they've subverted the very signals that protect other pitchers' arms.
Be careful, Lance Lynn, is all I'm saying. Feel free to continue striking batters out.