Someone Reversed Blake Treinen’s Polarity

Blake Treinen has spent an entire career as one of the best sinker-heavy relievers in all of baseball. Since his debut, he’s been one of the best relievers in baseball — period. That sounds like hyperbole but it isn’t. From 2014 through 2022, he ranked ninth in FIP-based WAR and fourth in RA9-WAR among all relief pitchers. He also ranked second in groundball rate among relievers who threw 400 or more innings. That’s elite performance, and he did it with a consistent attack of sinkers and sliders.

As his career has worn on, Treinen has made one big shift: He started throwing a huge sweeping slider. He was an early poster boy for the sweeper revolution. From 2014 through 2020, his slider averaged about an inch of horizontal movement. Starting in 2021, he changed the way he threw it, and that number blew up to nearly seven inches. That turbo-charged his strikeout rate, and 2021 was one of his better seasons despite intermittent command problems.

Those two things encompass most of what people know about Treinen. He gets a ton of grounders and he throws a big old sweeper. In fact, he was at the vanguard of a pitcher type that now seems to populate every major league bullpen: the sinker/sweeper righty. You can picture this guy, even if you don’t know his name on every single squad. He lives on the east/west plane, and produces plenty of ugly swings and probably a hit batter or two when his sinker veers into the righty batter’s box seemingly out of nowhere.

Treinen missed most of 2022 and all of 2023 with an unending array of injuries. He dealt with a capsule tear in his shoulder. He had surgery to repair both his rotator cuff and his labrum. He cracked two ribs and bruised a lung when he got hit by a line drive in spring training while attempting his return. It felt like he might never return, or would be a shell of his former self if he did. We’ve seen it happen to pitchers enough times that it’s never surprising, only sad.

Good news, though. Treinen has come back just as effective as ever. His velocity is down a few ticks, but his fastball has the same sinking action as always and his slider is moving even more than it was before he got injured. Through 17.2 innings of work, he looks like the same old Treinen – with just one slight exception.

Fantasy analyst and FanGraphs alum Brad Johnson pointed the change out to me a few weeks ago, and it’s one of those things that, once seen, can’t be unseen. Treinen is still striking out a ton of opposing hitters. He still occasionally struggles with walks. He still throws his sinker a third of the time, his slider a third of the time, and a cutter and four-seamer to fill in the gaps. But he’s racked up 18 fly balls and only 16 grounders so far, and it’s hard to think of anything less Treinen-y than that.

I know what you’re thinking, because I was thinking it too. Say it with me now: small sample size theater. Anyone can do anything in 20 appearances. Wake me up when he runs these rates for a year or two. There’s one problem with that: the evidence. Here’s Treinen’s groundball rate, in rolling 20-game segments, for his entire career:

This isn’t just business as usual. So I thought I’d look into what has changed, and whether we can learn anything broader from this development. After all, lots of pitchers across baseball are following the rough Treinen blueprint. Could the same thing be in store for them?

Treinen’s sinker is still a grounder-inducing pitch, but it certainly seems to be less so than before. In his career, he has a 65.3% groundball rate on the pitch. He’s down to 58.8% this year, which doesn’t seem like a big gap, but that underscores the change. One way of looking at it is that his ratio of grounders to fly balls has declined from 4.66 to 2.5. Or maybe this will do it for you: From 2015 through 2022, the average launch angle against Treinen sinkers was -1. In other words, the average hit was pounded downwards. That’s not quite the best in the game, but only the best sinker throwers rack up numbers below zero. Clay Holmes had the heaviest sinker in that time period at -8, while Logan Webb and Framber Valdez are each at -3. Marcus Stroman is at -1, Ranger Suarez at -2. Treinen fit right into that cohort.

This year, the average launch angle against Treinen sinkers is up to nine degrees. Batters just couldn’t lift his sinker before; this year, they’ve already hit five balls at 30 degrees or higher. That’s a full year’s complement of fly balls for Treinen.

I’m admittedly delving into tiny samples at this point, but Treinen is throwing his sinker up in the zone more than ever before. This year, 23% of his sinkers have been up in the zone; his highest single season before 2024 was 18.5%, and his career average was 13%. High sinkers are perfectly fine pitches – they just work differently. Those fly balls that opponents have hit against Treinen have been pretty awful this year, in fact: four harmless outs and a ball that Teoscar Hernández dropped for an error.

Treinen’s sinker still grades out well on every pitch model I could scrounge up. He’s still killing its natural backspin to an impressive degree, and it still explodes to his arm side. He’s just spotting it in different places, and while he’s still getting great results, they look different than they did in the past.

That brings us to Treinen’s sweeping slider, which is also producing fly balls in a way he just didn’t in the past. This time, though, the culprit isn’t mysterious. Sweepers make for popups. That’s a feature, not a bug. The pitch drops less than you’d expect for a breaking ball and tails away from same-handed hitters, which results in weak elevated contact.

The Treinen I picture, the guy who closed for the A’s, didn’t throw this slider. He threw a conventional gyro slider, with little horizontal movement and some downward break. It fell as much as the current one despite a five-mile-an-hour velo advantage. The new one should fall farther, since it has more time for gravity to work, but its movement just isn’t the same. The result is a lot of swings under the ball. Sliders are supposed to fall more than Treinen’s does.

If you’re looking for the mathematical expression of that thought, it’s this. Treinen’s old slider, which he threw from 2014 through 2020, produced a 2.34 GB/FB ratio. It was a heavy pitch, just like his sinker. His new slider, from 2021 to present, checks in at an even 1.0. Both pitches have been quite effective, with a slight edge to the new one. But his new sweeper gets to those similar results in an extremely different way, with popups and whiffs instead of grounders and whiffs.

Finally, there’s the matter of Treinen’s cutter. He dabbled with the pitch in Oakland, but started leaning on it more after joining the Dodgers. It’s a logical move, because neither of his primary pitches are incredible against lefties. From 2014 to 2020, he threw 63.1% sinkers to lefties. Then the Dodgers got serious about avoiding platoon disadvantages with a sinker, and his usage has dropped to 18.5% since. Something has to fill that void, and in this case, it’s the cutter.

Treinen’s cutter isn’t a particularly standout pitch, but he still throws it more than half the time against lefties. It doesn’t have notable ground/fly splits, and batters have only put eight of them in play this year anyway. But it’s just another way that he’s made completely logical changes to his game that lead towards more fly balls and fewer grounders. From 2014 through 2020, Treinen threw 425.2 innings, and coaxed 181 lefty groundballs with his sinker. In the 95 innings he’s thrown since then, he’s allowed exactly one lefty to hit a grounder off of his sinker. They simply don’t get to see the pitch enough to do much with it.

Is it a coincidence that GB/FB ratio is at its lowest point in our 2002-present database? Clearly not, and you can’t explain all of it with changing hitter behavior. Sure, hitters are trying harder than ever to get the ball in the air, but pitchers have a part to play too. Sinker/slider guys are increasingly using their pitches to get weak elevated contact instead of just fitting one cookie-cutter mold. Treinen is an example of the broader trend: use your pitches to get outs, not to fulfill some generic ideal of how things should work. He’s still the same guy – and yet very different at the same time.