Sinkers, Change-ups and Platoon Splits

You’re a pitcher? You need a change-up.

That automatic response seems reasonable enough given the state of modern pitching analysis. You’ve probably heard it plenty of times about pitchers like Justin Masterson or Chris Archer. After all, the change breaks away from opposite-handed hitters and helps pitchers neutralize platoon threats.

But you know what? There’s another pitch that breaks away from opposite-handed hitters: the two-seamer or the sinker, whatever you want to call it. And yet lefties love sinkers from righties. So why do two pitches with similar movement have such different results?

It’s not that change-ups and sinkers are exactly the same, but arm-side run is a rare thing, and they share it. In fact, look across the league at the average horizontal movement, and you might notice something.

RHP	Two-Seamer	Cutter	Splitter	Sinker	Slider	Curve	Change
X-Movement	-8.2	0.6	-5.4	-8.5	2.6	5.6	-6.5

The sinker and the change-up are the only pitches that have arm-side run, really. The splitter is a change-up for all intents and purposes (often called a split-change), and the two-seamer and sinker are similar if not the same pitch.

And yet the platoon splits on the two pitches are fairly different. Lefties had a .767 OPS against sinkers from right-handers last year, while they only managed a .713 OPS against change-ups from right-handers last year. Here’s the long version, with the league average platoon split added so that you can see that these two pitches work differently in practice.

	AVG	OBP	SLG	OPS
Sinker v RHB	0.245	0.329	0.364	0.693
Sinker v LHB	0.258	0.363	0.404	0.767
League Ave v LHB	0.259	0.329	0.412	0.741
Change v RHB	0.231	0.314	0.380	0.694
Change v LHB	0.240	0.330	0.383	0.713

I thought I’d ask a few pitchers about the phenomenon.

Rick Porcello actually developed a curve ball last season because he saw that his sinker and change-up were so similar. Having two primary pitches with the same movement “just makes it easier for hitters to hang out over the plate and go the other way,” Porcello said before a game with the Athletics in May. “It just looks too much like the same thing all the time.” Developing the curveball gave him a different break, and a pitch that was 10 mph to 14 mph slower than his fastball (his change-up only comes in 6-8 mph slower).

Sean Doolittle has been dominant with one pitch, and he’s throwing the slider a bit more this season, but the A’s new closer would still like to throw a change-up. Yes, both pitches run away from the opposite hand (in Doolittle’s case, the righties), but there’s something different about the way batters see the change-up. They try to get out there with their bat, and then… “they run out of bat,” said Doolittle. The combination of speed and movement means that they can’t wait long enough, and there’s no contact to be made once the pitch gets to the plate.

Brandon McCarthy has long sought a change-up ever since he dropped his original change-piece and went over to a steady diet of sinkers. He thought the main difference was the change in speed. “A change-up is still a change-up — it’s just supposed to be not there, whether it’s missing completely or it’s just off the end.”

Could a pitcher just throw the two-seamer slower? McCarthy thought that his teammate Trevor Cahill does that with some success, and the velocity chart on his sinker does show an eight mph spread on the pitch. But that’s a singular skill, as McCarthy himself admitted. Maintaining similar arm speeds on different pitches is hard enough to do without actively trying to throw one of the pitches at two different speeds.

It’s obvious that change of speed is part of the equation, but not every change-up and fastball pairing features a large gap in velocity. Felix Hernandez and Stephen Strasburg both own top-five change-ups, and their gaps (3.0 and 6.4 mph respectively) don’t fit the conventional wisdom that desires a ten-mph gap between the two pitches. Of course, Harry Pavlidis has shown us that hard, firm change-ups have their place (ground balls), but it goes to show that velocity doesn’t explain everything.

Brian Bannister says the y axis is a big part of the change-up’s success: “A two-seamer usually is a flatter spin-axis derivative of a pitcher’s standard four-seam fastball. A change-up can be a completely different pitch entirely.” But two-seamers are tough to throw effectively, Bannister adds. “Hitters like pitches with backspin because they want to hit the bottom half of the ball,” he says. “Very few pitchers who try to throw two-seamers are able to put the necessary sink on the ball to be successful at the major-league level. To most hitters, an average two-seamer is just a slower four-seamer. The pitcher doesn’t gain much of an advantage by throwing it because it only adds some lateral movement. However, almost all pitchers are eventually able to develop some form of change-up that reduces velocity, reduces spin, and/or adds random movement to the ball, and this can drive hitters crazy.”

To Bannister’s point, let’s look at the vertical movement for those same pitches from righties. That same table from above, revisited for the y axis.

RHP	Two-Seamer	Cutter	Splitter	Sinker	Slider	Curve	Change
Y-Movement	6.3	6.1	2.9	4.3	1.4	-5.6	4.3

Another surprise. Change-ups, on average, have the same vertical movement as sinkers as well as similar horizontal movement.

Back to velocity, then? Even the average change-up goes 83.2 compared to today’s average fastball at 91.6.

Porcello felt the change-up’s excellence was about that difference, about timing. Thinking about hitters, the Tigers’ pitchers said that “all their timing comes off the fastball — you’re timed to hit the fastball.” And it’s no surprise there’s a bigger platoon split on the fastball, according to Porcello; “Overall, hitters hit fastballs better than any other pitches — but when they’re worried about your good fastball, they can’t sit on your offspeed stuff, because then they can eat you up with fastballs.”

Let’s add one pitch back into the equation that should help put all of this into focus. The four-seam fastball. The most-thrown pitch in baseball actually has six inches of arm-side run on average, meaning that the difference between a two-seamer and a four-seamer is maybe less than we assume.

That similarity, and perhaps the hitting approach that is timed to the fastball and doesn’t leave enough bat for a change-up that’s fading away from the lefty on the outside, seem to suggest that the change of speed — with the same arm speed — is the major separator between the two-seamer from the change-up.

To some extent, that’s surprising. After all, when you think of the best change-ups, you think of the darting, diving, off-the-table movement. But the (relative) number on the radar gun might be even more important, especially if you’re a righty pitching to a lefty.