Hildenwho? Was my thought when I first saw Trevor Hildenberger pitch for the Minnesota Twins. I hadn’t heard much about him aside from rumblings he was performing consistently well at AAA Rochester. The then 26 year old was drafted in 22nd round of the 2014 amateur player draft out of UC Berkley. He was pick 650 overall, but who’s counting? This was all news to me. The Twins had been through a dearth of ho-hum relievers on their way to a typically mediocre bullpen. I didn’t pay much attention to Hildenberger, thinking he might not last long in the majors. What a considerable miscalculation that was.

Hildenberger had good MiLB numbers, but I had no idea how dominant he was. In any MiLB stint in which Hildenberger pitched at least 20 innings, he never had a K/9 of under 9.6, and never had a GB% lower than 53%. He topped out at 11.8 K/9 at low A. His GB% peaked at 67%. To put that into some major league perspective, only 4 guys who threw at least 40 innings in 2017 had a GB% higher than 67% (one of whom, Scott Alexander, the Dodgers saw fit to trade for as a replacement for Tony Watson in their bullpen). Granted, Hildenberger was at high A, but the signs were promising. Hildenberger had consistently shown an ability to do two things which in combination can make a reliever elite; get lots of strikeouts and induce a ton of ground balls.

Fastforward to June of 2017 and Hildenberger makes his MLB debut. Before continuing, it’s worth pointing out that Hildenberger has a pretty small MLB sample size to date. This is therefore more of a commentary on what has been, rather than a prediction of what will be. In 2017, Hildenberger finished his rookie season with a GB% of 58.8%. This was good for 13th among relievers who threw at least 40 innings. If you add the criterion of relief pitchers who had K/9 greater than 9, Hildenberger is one of 23 relievers across major league baseball to combine these rather useful traits (he ranks 10th by K/9 from the qualified list). Hildenberger ranked right above Bryan Shaw, who just signed a 3 year pact with the Rockies for $27 million, (Hildenberger will make almost nothing by comparison in 2018). The top two names on this list are Nationals Ryan Madson, and Pirates Felipe Rivero. Both Madson and Rivero were elite relief pitchers last year, combining for a WAR of 4 and averaging an xFIP of 2.72 between them. Madson and Rivero are a fascinating duo of names in part are so entirely different from Hildenberger, both rely heavily on their velocity. So what makes Hildenberger so good? And what makes him able to generate such a high level of ground balls and strikeouts?

Velocity

On a surface level, Hildenberger is unusual when you take a closer look at his velocity as a pitcher. At first glance, Hildenberger seems like a soft tossing side-armer. This is not the case. Despite not using it much, Hildenberger’s fastball showed a steady increase in velocity from June to October in his first big league season, from just under 91 mph in July, up to a season high of 94.78 mph in October.

The aforementioned Felipe Rivero and Hildenberger share a fascinating skill, an excellent changeup. Rivero threw his changeup around 20% of the time in 2017, to Hildenberger’s 35%. Both however, are a significant value add for each pitcher. Hildenberger and Rivero have a similar velocity differential between their highest and lowest velocity pitch (between 15-16 mph on average). Hildenberger’s approach differs because he throws his fastball just 13% of the time. Contrarily to the majority of pitchers who use their fastball to set up their off-speed pitches, Hildenberger is constantly working off-speed (35% changeups) and uses a surprisingly competent fastball to keep hitters honest. While Hildenberger’s sinker and changeup are vastly superior pitches, his use of velocity is an example of how his unconventional means keep hitters off balance.

Release Point

The next aspect of Hildenberger’s unusual approach that merits some thought is his release point, or rather, points. Simply put, a release point is the combination of horizontal and vertical coordinates from which a pitchers releases the ball. Higher release points tend to produce more sink, more extreme horizontal release points tend to create more horizontal action throughout the plane of the pitch.

The chart below shows Felipe Rivero’s vertical release point (in feet) throughout the 2017 season for his four pitches. Many pitchers, like Rivero have pretty consistent release points, born of mechanics which have been tuned and honed over many years. Rivero’s fastball has an average release point of 5.69 feet, while his slider has an average release point of 5.43, a differential of .26 feet between his highest and lowest release points. By contrast, the average vertical release point of Hildenberger’s fastball is 5.6 feet, while his average release of his changeup is 4.13 feet, good for a differential of 1.47 feet. Hildenberger has an incredibly low and difficult to pick up release point for pitches he throws 70% of the time (his sinker and changeup), simply because hitters rarely see baseballs coming towards the strike zone from such a height, or lack thereof. Additionally, Hildenberger has a huge differential between his different arm slots. In essence, facing Hildenberger throwing a fastball versus Hildenberger throwing a changeup is like facing two completely different pitchers in the same sequence of pitches.

While the horizontal point of release does not make for quite such an impressive contrast, a similar disparity exists, both comparing Hildenberger to other pitchers and within his own pitch mix. In short, Hildenberger’s inconsistency in his vertical and horizontal release points go a long way to overcoming the limitations of his lack of velocity.

The Twins seem likely to let Fernando Rodney handle ninth inning duties as closer in 2018. Hildenberger made an incredibly impressive debut in 2017 using extraordinary means to pile up extraordinary results. He will likely assume the mantle of the relief pitcher used most frequently in high leverage situations moving forwards. This is a spot Twins fans should feel comfortable with ‘Hildy’ occupying. After all, he’s already proved he can. Minnesota, get to know your real bullpen MVP.