Fix Corbin Burnes's Sinker, Win $100 Million

[Matthew Trueblood]

In 2020 and 2021, Corbin Burnes might have been the best pitcher in baseball. If he took a small step backward in 2022, it was just that. In 2023, though, the Brewers' ace experienced some genuine adversity. Whether he regains his previous form in 2024 could be a $100-million question, and it could come down to a pitch he uses relatively rarely.

Image courtesy of © Jeff Hanisch-USA TODAY Sports

For all the consternation around Burnes pounding the zone with his cutter and giving up too much hard contact, the fact is that he has remained overpowering--at least against left-handed batters, who get stumped by that cutter. Lefty hitters had a .263 wOBA against Burnes in 2020, a .248 in 2021, a .269 in 2022, and a career-low .236 in 2023. He hasn't lost a thing against opposite-handed batters. He still racks up strikeouts, and when lefties do make contact, it's often weakly hit and often on the ground.

Things are different against righties, though. Against them, Burnes has gotten steadily worse since his COVID-shortened breakout: a .207 wOBA in 2020, then .215, .264, and in 2023, .295. Even that figure isn't atrocious, but it's the difference between a very good pitcher and a truly great one. Moreover, it could have been much worse. Burnes's strikeout rate against righties plunged from over 30 percent in each of the three previous seasons to a pedestrian 22.2 percent this year. His ground-ball rate plummeted, and opponents hit the ball hard much more often. 

I can sum the problem up thusly: Unlike in his previous, better seasons, Burnes simply couldn't command his sinker in 2023. It really got away from him, and ended up in much more hittable places.

That's not the only thing about the sinker that has changed. It's lost about 1.5 miles per hour, from almost 97 to 95.3, since the start of 2021, which has some unavoidable effects. It's also gotten a bit heavier. It sinks a bit more than it has in the past, which makes sense, for two reasons: 

1. That little bit of lost zip means he's giving the ball a little less resistance to gravity; and
2. He's slightly lowered his release point on it.

The latter change is so subtle you could easily miss it. Burnes isn't dramatically lowering his arm slot on the sinker. He's just not staying quite as upright through his delivery.

2021 Sinker Release

2023 Sinker Release

He's releasing the ball a hair later, so he's getting greater extension toward home plate at release. 'Greater' doesn't always mean 'better,' though. That later release isn't a conscious choice. It's a systematic error in timing. Burnes is releasing the ball lower, more in line with his body, and closer to home, and the result is a sinker that sinks more, but runs less horizontally and stays over the plate too often.

It's not as simple as giving up on that pitch, even though Burnes has three other formidable weapons for righty batters. The cutter, the curveball, and the slider all work to the outside part of the plate to righties. Burnes uses the sinker to keep them honest inside. He has felt, especially, like his cutter sets up his curveball, but his sinker sets up the slider.

As has been well documented, though, Burnes tweaked that slider in the middle of 2023, engineering more of a sweeper-like offering. It's slower and has more horizontal movement, and while the natural thought is that a horizontal slider works well with a sinker, that's less true given Burnes's spin signatures and arm angle. From him, the new, sweepier slider has pretty good spin mirroring with the cutter, and it might be best to simply try tucking the sinker farther back onto the shelf and unloading more cutters, curves, and sliders. 

That's what Burnes did in September 2023. That was his best month in terms of strikeout rate, strikeout-minus-walk rate, and soft contact rate against righties during the season, though the size of the sample admonishes us against drawing firm conclusions. He certainly could be a better version of himself than we saw, on the whole, just by using the sinker less often.

To really recapture the brilliance of 2020 and 2021, though, Burnes needs that pitch. To be in line for a Gerrit Cole-type contract next winter, as he still harbors some hope of doing, he has to get the feel for that pitch back. It means rediscovering his release point, in all three dimensions. It means better command than ever, because he's lost a little bit of the power that gave him a wider margin for error a couple years ago. It's a tall task, but if Burnes manages it, he could be a full-season version of CC Sabathia for the Brewers: an awe-inspiring playoff ace, opening up his engine to full throttle right alongside a team trying to shake off a legacy of October futility.

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