Trueblood: The sinker doesn’t play well with others

From Matthew Trueblood at Baseball Prospectus on September 19, 2017:

Earlier this month, Jeff Sullivan of FanGraphs wrote about a global trend in pitching throughout MLB. Pitchers are throwing fewer fastballs (as a percentage of total pitches) than ever before, at least for the decade during which we have reliable data. What Sullivan found is that, while it’s true when considering fastballs as an undifferentiated set, it really doesn’t capture the whole truth. He looked at Pitch Info, which (correctly) tags four-seam and two-seam fastballs (the latter often being called, and being called from here onward in this piece, sinkers) as separate pitches, and found that the loss of fastballs is almost all sinkers.

The league is increasingly selecting for pitchers who use four-seam heat to work up in the zone, frustrating batters’ efforts to attack the ball on an uphill plane and get it in the air—or at least, that’s the theory Sullivan puts forward for the shift. I mostly agree. There’s no doubt in my mind that the move toward four-seamers and away from sinkers is at least partially in response to batters making changes geared toward handling those sinkers, and punishing them. (Recall that, as recently as 2013-2014, Ray Searage’s Pirates were at the cutting edge of run prevention because they so consistently pounded hitters with sinkers that ran in on their hands or nipped the bottom of the strike zone; there has been ample incentive for batters to adjust in turn.)

However, I see at least a couple of other reasons why sinkers are disappearing league-wide, even as four-seamers largely maintain their standing as the official primary pitch of baseball, in this era of such highly evolved combat between batters and pitchers. The way the sinker interacts (or fails to interact) with other pitches in pitchers’ arsenals and our changing understanding of the factors that lead to elbow injuries are helping drive the league toward more four-seam fastballs, and fewer sinkers.

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Originally published: September 19, 2017. Last Updated: September 19, 2017.