It seems a long time ago now, but Clay Buchholz was once the top prospect in Boston's farm system. He was a five-star caliber starting pitching prospect, one with a deep repertoire, impressive velocity, and a no-hitter in the majors to his credit after just a handful of innings at the level.
That version of Clay Buchholz had a hammer curve that he utilized often -- the plus-plus bender was considered his best offering. Over time, he moved more towards a fastball/slider combination, with a filthy change-up in the mix to boot, and that curve that, as Kevin Goldstein put it, "batters falling down while trying to hit it" wasn't phased out, but was pushed aside.
Buchholz has continued to evolve his pitch selection since becoming a full-time starter in the majors. His slider changed grips and forms two years in a row, moving from an 81 mph breaking ball into the very similar 90 mph cutter that he features today. He no longer throws just the four-seam fastball, as he has a sinking two-seamer that induces weak contact and the grounders that are his lifeblood. Whereas he used to rely on his secondary offerings too much -- pitching backwards, as it were -- he's become more aggressive the past few years, and leaned on his groundball-inducing fastballs.
The plan for 2012 seems to be reintroducing the curve in order to give him another weapon. He threw it often in 2008 -- 20 percent of the time -- but once the slider was put in the rotation, usage of the bender dropped to 11 and 13 percent in 2010 and 2011. Since his slider is no longer a slider, taking on that harder, tighter cutter movement and speed, additional use of that hard curve would, in theory, give hitters just one more thing to worry about.
The last few years, it's most effective use has been as something batters foul off. (Data courtesy of Brooks Baseball):
This table shows z-scores, so you can see how many standard deviations about the mean Buchholz's pitches are in a variety of categories. In his career, his curveball hasn't been great at inducing swings-and-misses, but it has kept hitters off-balance far more than any of his other pitches, according to foul balls per swing. It's also been effective at inducing grounders when it hitters make more solid contact on the pitch.
The other area in which the curveball excels for Buchholz is as a pitch that earns him called strikes. He freezes hitters with it more than he gets them to miss. The problem is that it's also the pitch Buchholz misses with the most: in 2009 and 2010, it was called a ball more than half of the time, and while better in 2011, still went for a ball 43 percent of the time it was thrown.
More curveballs are a good thing, but they might not be a great thing. Buchholz used the curve more back when he wasn't great at attacking hitters, when he was less aggressive with them. If he can figure out a way to utilize it more often without sacrificing the efficient plan of attack he's already succeeded with, then by all means, throw more benders. But if more curves means longer plate appearances, more balls, and more hitter's counts that Buchholz has to fight back from, then it should continue to be the pitch he features the least often.