It’s time to learn about Trevor Hildenberger

With the hope that I have built up enough baseball blogging capital to say this, I would like to inform you that the Minnesota Twins have one of the most interesting relievers in Major League Baseball. For starters, the name Trevor Hildenberger is award winning. No, really. Only three other pitchers have appeared in a game this season with a last name 12 characters or longer. Asher Wojciechowski takes home the ultimate prize with 13 letters, while Drew Steckenrider and Al Alburquerque are tied with “Hildy.”

Now that I have gotten a good jump on my weekly character quota, let’s talk about Trevor Hildenberger as a pitcher. He fits the classic Twins’ mold — pitchers whose goal is to limit walks and induce weak contact — while also managing to strikeout a ton of batters. In a bullpen where the overall strikeout rate is below 20 percent (worst in Major League Baseball) Hildenberger stands strong, striking out 26.5 percent of the batters he has faced. That rate looks even better when considering that, in the 24 ¹⁄₃ innings he has notched since his MLB debut in late-June, Hildenberger has walked just three batters (though he’s also hit three). Oh yeah, and a 60 percent groundball rate isn’t too shabby either.

It all culminates when you take a peek at Hildenberger’s shiny 2.95 DRA, and you’d be right to think the Twins have a budding relief ace in their midst. But while these stats do a good job at determining skill and true talent, let’s break him down by looking at process rather than outcome. Hildenberger has been good to this point, but digging into the why is crucial for a player with such a short track record. Is there something about Hildenberger that stands out, or are the outcomes steeped in noise?

I’ll assume you haven’t had the pleasure of watching a pitch from the Minnesota Twins’ setup man this season but, to venture down this path, you must get familiar with his stuff:

Sinker

Changeup

Slider

Fastball

We’ll get to the slider and fastball later on, but Hildenberger takes advantage of his sidearm slot by throwing either a sinker or changeup about 80 percent of the time. It is not unheard of for sidearm/submarine-pitchers to do this, but, staying true to the Twins Way, Hildenberger’s velocity is well below average. His sinker obtains the velocity equivalent of a lukewarm summer day, mid- to high-80’s (88 mph on average), while his changeup hovers around the mid-70’s. Actually, the best descriptor might be what Brooks Baseball says about each pitch on Hildenberger’s landing page:

“His sinker is so slow that it is substantially gravitational… His change comes in below hitting speed.”

So, in case it was unclear, Hildy throws rather slow for the Major Leagues. However, this isn’t a terrible thing. What sets Hildenberger apart is the sheer movement on these pitches. Brooks Baseball has a nifty Z-Scores tool that lets you compare just how unique certain aspects of pitches are. Utilizing this tool, we see that the vertical movement on his changeup is -3.05 standard deviations away from the mean, while his sinker is -2.63 standard deviations away.

These values are negative because, in the world of vertical movement, pitches are tracked assuming no spin (i.e. gravity doesn’t play a role). This essentially means that a negative z-score on vertical movement means less spin, more drop. With gravity, however, Hildenberger’s changeup averages 46.51 inches of drop, while his sinker owns a 31.70 inch mark.

Non-technical translation: that is some serious downward movement.

The mixture of low arm slot, low velocity, and low spin rate all surely play a role in generating that wicked sink. And while Hildenberger isn’t just lobbing it in there, you might find it strange for a pitcher with this particular repertoire to find success in an era of high velocity relievers. It is strange, but what separates Hildenberger from similar pitchers is that he possesses an ability to have his sinker and changeup work in tandem with each other. Essentially, he thrives on deception and an ability to prevent the hitter from deciphering whether a given pitch is a sinker or changeup.

The real difference between a sinker and a changeup lies in velocity and vertical movement. Thanks to a lower spin rate, changeups tend to be slower and with a little more drop than their sinker counterparts. As the old cliché goes, if you can make your changeup look like a fastball, you’ll have success. This deception is exactly what Hildenberger is doing a fantastic job of.

To confirm that this is what Hildenberger is doing, we’ll use the pitch pairs data that Baseball Prospectus rolled out last winter. It focuses on three key aspects of a pitch: the pitchers release point, the tunnel point (which is essentially halfway to the plate, and the point at which the hitter decides whether to swing or not), and the plate. Narrowing it down to those three points, you can get an idea of where two pitches deviate from each other, and if that occurs before or after the hitter theoretically decides to swing. The theory then is that when two pitches don’t noticeably differ at the release or tunnel point, but do at the plate, the pitcher is successfully “masking” a pitch.

Things like release:tunnel (the ratio of a pitcher's release differential to their tunnel differential) and break:tunnel (the ratio of post-tunnel break to the differential of pitches at the Tunnel Point) help us see this through the creation of a rate stat, while release, tunnel, and plate differential help us see this on a more raw-ish level. Post-tunnel break is another helpful stat here, as it measures the difference in break between two pitches following the point when the hitter has decided to swing. So where does Hildenberger sit in all this?

Bingo. In terms of following up his sinker with a changeup, and vice-versa, Hildenberger is one of the best in the league at hiding it from the hitter. The sample-size is small, since it only extends to June, but an ability to thrive on deception is a crucial part of his success. Neither pitch could likely survive on their own, but when working in tandem they have devastating consequences. And the threat of not recognizing either pitch extends past following one up with the other.

He has thrown 27 sinker-sinker, and 19 changeup-changeup pitch pairs. Because the speed difference is so large, it is crucial for a hitter to recognize the pitch early on to avoid mistiming their swing. Hildenberger’s ability to intertwine these two pitches makes up, in this regard, for his low velocity. His pitches might not get to the plate quickly, but he’s still forcing batters to make decisions faster than their comfortable with. Oh yeah, and just when you think you’ve figured out those pitches, he isn’t afraid to mix in a four-seam fastball from an over-the-top delivery, a pitch that reaches much closer to the mid-90’s which he uses as somewhere of an out-pitch, and is dangerous when preceded by a changeup.

But delivery is one part of the process, location and command is another. Command is essentially what Hildenberger’s success hinges on, because you can only get so far on deception alone. Both his sinker and changeup own a GB/BIP over 60 percent (with the latter over 70 percent), and this comes from where in the zone he likes to pitch. His ability to command the bottom-third of the strike-zone is crucial, and has led to a ton of grounders:

This is something he mentioned in an interview with Mike Berardino in late July:

“I try to keep the ball down in the zone,” he said. “I take a lot of pride in keeping the ball in the ballpark, and also forcing contact — try to get groundballs as much as I can, let my defense work. That’s my track record, and I hope to continue that.”

But it’s not just words; Hildenberger has followed up that statement (plus another one he made later in the interview about not allowing home runs) with a clear, and rather amazing, track record. Across 171 ²⁄₃ innings in the minor leagues, he walked just 26 batters (!!!) and surrendered four home runs. Scouting the stat line is verboten, of course, but that is utterly remarkable. His time in the Major Leagues obvious comes with the small sample-size caveat, but pitching well is nothing new for Hildenberger; the only thing new is the size of the stage.

He notched his first career save on August 13^th against the Detroit Tigers, and I’m willing to bet it won’t be his last. The risk, of course, is that Hildenberger has a smaller margin for error than most. On days where his command or an ability to make his sinker/changeup look similar struggle, his mistakes are much easier to hit than those of, say, Noah Syndergaard, Rasiel Iglesias, Nate Jones, etc. Then again, that’s not too much of a secret. Command/deception pitchers come around all the time, and they’ve had successful careers as closers before. With that said, the feel for a repertoire like this, knowing exactly when to throw what pitch, is what makes everything tick — and the youngster appears to have it.

The Twins, per usual, have a quirky pitcher in their midst. This one, however, has the potential to be dominant. As long as they keep Hildenberger away from Jose Iglesias, who has homered twice off him, things look bright. Whether he becomes the relief ace or stays in a setup role, he will surely factor into their run at the second American League wildcard spot.

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— All stats taken before play on 8/18

— Z-Scores taken from Brooks Baseball are considering all right-handed pitchers who have thrown a given pitch at least 100 times this season