Clay Buchholz has the best strikeout and swinging-strike rate of his career! Clay Buchholz has a new changeup grip! Therefore his strikeout rate must be because of his new changeup? Maybe, but it’s not a linear thing. Nothing in baseball ever is.

The Red Sox pitcher did change from a four-seam changeup grip to a two-seam grip — look at Jake Peavy’s versions for a reference point — and the difference has been stark. Read the excellent Brian MacPherson on the subject, and then look at the change in horizontal movement from the changeup.

When Buchholz has thrown his four-seam changeup, it tended to have little side-to-side movement. It instead would mimic the path of his four-seam fastball and then dive straight toward the dirt as it neared the plate. What the two-seam changeup does is mimic the path of a two-seam fastball, fading horizontally at the end of its flight — in on righties, away from lefties.

It’s remarkable how the words pair with the pictures. The changeup’s horizontal movement just jumped right over and now matches the movement on the sinker instead of the four-seamer. In pictures, you see it easily, too. The old changeup (left) and the new one (right):

And results have followed suit. The two-seam fastball is known more for grounders, and so his new two-seam grip has a better ground-ball rate this year (63%) than last year (48%). Whiffs? The four-seamer is better for whiffs, and so the whiff rate on the changeup this year (22.5%) is lower than last year’s (24%), but not by much. All told, it’s a better pitch now.

But you can tell from that last stat that it can’t be responsible for his new strikeout rate by itself. The changeup is actually getting fewer whiffs overall than it used to. So we have to look for more clues on Buchholz’s whiffier results profile this year.

There’s that tiny bit of velocity boost across his pitching mix. His curve is humming along faster than it ever has before, and the cutter and fastball are faster than they’ve been in the last three years. But these are all marginal, on the order of 0.5 mph at most.

And yet… the cutter and sinker have almost doubled their previous whiff rates. That’s more than you’d expect from a marginal velocity increase. And there’s not a ton of movement or usage change for those two pitches, really.

Let’s double back to the changeup, because the difference there could have cascading effects. Look at Buchholz’s strikeout minus walk rate against lefties and righties, indexed to his career average — he’s taken a leap forward against one population. That’s listed in MacPherson’s piece as part of the reasoning behind the move, as the new fading change dives away from lefties.

Year Right Handed Hitters Left Handed Hitters 2008 72 106 2009 91 68 2010 100 51 2011 62 107 2012 83 80 2013 135 158 2014 128 90 2015 154 229

Buchholz has been better against both righties and lefties this year, but it’s obvious that the new change has given him more of a boost against lefties. The harder cutter is his best pitch against righties (20% whiffs), but the change is still useful (15% whiffs). Against lefties, Buchholz’s new changeup is his best pitch (26% whiffs), but the cutter is still useful (15% whiffs). He’s using the changeup twice as often against lefties this year (19% to 9%), so we’re starting to get the picture of a pitcher with a better arsenal to bust platoons. Even if the changeup has always been his best pitch.

Clay Buchholz has a new changeup. His new strikeout rate is probably a result of that new changeup, even if the changeup was always his best pitch, and he’s getting fewer whiffs on it overall. Baseball works in funny ways.