Why Can’t Anyone Hit Paul Sewald?

marc w · July 6, 2021 at 4:41 pm · Filed Under Mariners 

Sorry for the week off; I’m back from a road trip in Oregon. No, I wasn’t felled by the heat wave, though hanging in Portland last Sunday was an experience I can only describe as surreal. I just took a week off to hang in Central Oregon and jump into whatever stream or river presented itself. Some parts of this were in non-WiFi/cell service range, and while I could’ve/should’ve posted something in those areas that DID, I have to admit, it was kind of nice to shut all of it out. And hey, the M’s continue to play well, so that was something of a nice surprise to return to.

But enough about that. We need to talk about Paul Sewald. No, this is not a post I ever thought I’d write, but the 2021 NRI/minor league signing has quickly become one of the team’s best bullpen arms – the best, per Fangraphs, in fact. The M’s (like all teams) have seen something like this before, where an unheralded NRI gets great BABIP luck or strands a ton of runners, and it’s awesome to watch before regression spoils the party (Roy Corcoran is the classic M’s example). But at least thus far, that’s not been what’s driving Sewald’s results at all. He’s essentially doing it all himself, with a K/9 approaching *16*. He is bullying opposing hitters with one of the most untouchable – and strangest – pitches in the game: a 92 mph fastball.

There really isn’t anything that jumps out at you when you look at Sewald’s best pitch. By pitch type values, it’s the 5th best heater in the game on a rate basis, just behind Kendall Graveman, and somehow ahead of Jacob deGrom’s. It’s not thrown with elite velocity, and while Sewald generates above-average spin with it, he’s below average in spin efficiency, leaving him without elite movement. It’s thrown at an odd angle, as the side-arming Sewald releases the ball at around 4 and a half feet off the ground, quite a ways away from a more normal 3/4 delivery that’d come out at around 6 feet off the ground. But even there, side-arming FB/SL relievers are hardly rare, and it’s not a freakishly low release like Tyler Rogers has. It’s different, but not necessarily better.

Does he rely on pinpoint command? No, the guy sporting a BB% near 12% does not boast freakish control, and that doesn’t seem likely to change. Is Sewald’s Fastball relying on surprise? That is, is his slider the real weapon that batters need to be aware of, so they’ll take the odd fastball even when it’s over the plate? MLB’s swing/take stats show he’s done well in the heart of the plate, but that includes swings as well, and in any event, his slider’s been below-average this year. Sure, he’d upped his usage of it in the early part of this season, but over the course of the year, he’s going to the fastball more and more.

Sewald’s fastball has essentially average vertical break and a bit more horizontal run than average. That said, if anything, it’s slightly less than you might guess given that sidewinding motion. His slider has above-average spin efficiency, and mirrors his fastball’s spin pretty well, a point made in this great article by Michael Ajeto over at LL recently. With his arm angle, you’d expect lower vertical rise and more armside run, and you might expect even more now that Sewald’s lowered his arm angle this season from about 4.7′ to 4.5′.

But these skills and changes seem pretty middling given the sheer dominance that we’re witnessing here. Flattening his arm angle would be great if he was using that armside run and sink to send his ground ball rate through the roof. But no, the sidearming Sewald has a GB% below 27%. How does that happen? Because Sewald throws his fastball up in the zone.

That helps explain the GB% and we’ve known for a while that you can fractionally increase whiffs by throwing heaters up, but I don’t think it’s quite enough to explain how an NRI can pitch like early-career Aroldis Chapman for a few months. Deception is undoubtedly playing a pretty big role here, and that’s harder to measure, but I think the best way to explain this is to look for a comp: is there anyone else out there striking out a ton of batters with an underpowered fastball thrown high in the zone? Especially one that’s got low spin efficiency and thus without tons and tons of vertical movement?

Yes, there is. It’s a pitch I’ve been talking about all year, going back to spring training. This is Freddy Peralta’s MO. Peralta releases the ball just over 5′ off the ground, throws 93 with above-average spin, and has a velocity-adjusted-spin rate of around 25.5-26. Sewald’s a tick above 26, but they’re right there. When he came up, Peralta threw 75-80% fastballs, but he’s having his best season in 2021 despite reducing his fastball usage to around 50-55%. Peralta’s spin efficiency is 83.3, Sewald’s at 83.6 (ranking them 273rd and 281st in MLB).

I’d initially compared Peralta’s heater to his teammate, Josh Hader’s. But while there are some similarities, they’re really quite different. Hader has plus velocity, for one thing, and ranks #1 in spin efficiency, with 100% active spin. Still, the thing that jumps out at you is that both are able to throw them to batters who 1) know the pitch is coming and 2) know the general area that pitch will target.

It’s kind of wild to think of how many traditional nostrums of pitching these fastballs violate. You want a high-spin pitcher to improve their efficiency to generate more movement – but Peralta and Sewald don’t, and don’t have any reason to at this point. You want a pitch thrown with sidespin or from a low angle to sink and target the knees or a bit below – but Peralta and Sewald have made their mark by staying up. Everyone knows a low arm-angle pitcher, especially with a FB/SL repertoire, will face platoon split problems – but Sewald’s been *better* against lefties this year (small sample alert), and while Peralta has regular platoon splits, he’s effective against both lefties and righties.

So we’ve found a similar pitch, but I’m not sure we’ve found why they’re both so effective. I think there’s something confusing about the way the pitch behaves due to the amount of cut both Sewald and Peralta impart. They’re throwing high in the zone with a ball that doesn’t move the way traditional high fastballs do, and their arm angles heighten that sense of confusion. Craig Kimbrel has made a name for himself throwing high, low-efficiency fastballs up, and he may be an honorary member of this small club, but he also has plus to plus-plus velocity, so he gets there somewhat differently. The Pirates’ Richard Rodriguez is another low-grounder, high K (uh, until this year) pitcher relying on a 93mph fastball up in the zone, but he surpasses even Sewald in both spin and efficiency, and seems to have a slightly different approach based on throwing high *and away* fastballs to both lefties and righties, leading to a ton of opposite-field contact. Sewald’s doing similarly, but doesn’t have such a clear pattern by batter handedness. Still, Rodriguez doesn’t have the super-low release point that Peralta and Sewald use.

Ultimately, it’s probably a mix of his slightly higher velocity (something he flashed in 2019), some improved deception, and increased belief in his own fastball. Sewald’s throwing it in the zone more than ever, and thus is getting more swings than ever. The key question is, as always, can this continue? I’m not sure anyone can do *this* consistently, but it’s an approach that’s paying off and doesn’t scream luck. Sure, his 0% HR/FB ratio will change; you can’t get that many fly balls to stay in the park in 2021, especially without great command. But I think he’s a better true-talent strikeout pitcher than any of us ever imagined, probably including Sewald himself. Peralta’s up-and-down last few years (and Kimbrel’s as well) points to the fact that he will probably have some ups and downs, but Sewald seems like a legitimate late-inning arm for the M’s, and he’s been a key reason why they’ve been so good in one-run and extra-inning games.


One Response to “Why Can’t Anyone Hit Paul Sewald?”

  1. Stevemotivateir on July 8th, 2021 6:22 am

    I never would have guessed Peralta would be a comp, but this is explained well.

    Fans are probably wondering if Graveman will get traded. Maybe we should be wondering if Sewald could be moved for a starter in a sell-high move. With Muñoz and Giles to move forward with, I wouldn’t be surprised.

    For now I’ll just continue to enjoy watching him while nervously wondering if Kikuchi can maintain his success with lower spin rates.

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