40 in 40: Zac Grotz

Zac Grotz is no stranger to the grind: after being picked out of the University of Tennessee in the 28th round by the Astros in 2014, he only made it to short-season before taking his talents to independent ball. Spending parts of three years in the Frontier and Atlantic Leagues, the Mets snapped him up in June 2018, and he finished the year with their Single-A affiliate, making thirteen starts. Despite being over three years older than the average age in the Sally League, Grotz put up a not-so-great 4.61 ERA across eighty innings, although FIP was much kinder to him at 2.83. Although he posted a strikeout-to-walk ratio of nearly 7:1 and did a solid job of keeping the ball on the ground, he elected free agency at the end of the year, and Seattle signed him to a minor-league deal just five days later.

After a couple scoreless outings in big league spring training, Grotz was assigned to Double-A Arkansas, and after a move to the bullpen was one of the Travelers’ most dependable arms all season. His K/BB was over 6:1, his ground ball rate neared 60%, and this time around, his ERA matched his peripherals. In all, he posted a 2.51/2.68/2.31 pitcher slash, and got the call to the bigs on July 31st. Over five scattered appareances, he scuffled a bit, walking five in 7.2 innings to go with just seven strikeouts, and was optioned on August 24th. Roster expansion brought him back up in September, though, and he looked much improved after a brief stop in Tacoma. While the 4.66 ERA over 9.2 innings doesn’t jump off the page, there’s a good case that he was bit hard by bad sequencing luck: he held opposing hitters to just a .206/.282/.235 slash line, walked just three compared to eleven strikeouts, and saw more time in high-leverage situations (well as much as there were high-leverage situations for the 2019 Mariners).

Grotz mainly relies on two pitches: a four-seam fastball that sits at around 92, and a splitter at 82-83 with big late vertical break:

He also flashed a sinker, slider, and curve, but the four-seam/split duo combined for over three-quarters of his offerings. He actually threw more splitters than four-seams, and mixed them pretty well:

Baseball Savant

His splitter got boatloads of weak contact - that barrel rate of 0.0% is very pretty - and he was able to worm a ground ball out of it nearly 70% of the time. While he can get plenty of whiffs from it, he struggled to throw it in the zone last year, with just 32% landing in the zone. He’ll also abandon it the further he gets behind in the count: notice how on 3-0 he only threw the four-seam, and even at 2-0 he went to the split about one out of six times. Throw your best pitch even more, Zac!

The good news is that even though he doesn’t get a ton of whiffs on his other pitches, each and every one of them were excellent at inducing grounders: his average launch angle was a teeny-tiny 2.5 degrees (!), and the highest was from his four-seam at just 9. With this in mind, it’s not surprising that he didn’t allow a homer across his 17.1 big league innings and put up a ground ball rate of 67.4% - which would have been third-best among qualified relievers last year. It would be foolish to expect him to keep that up all year, but his process feels a lot more sustainable than say, Sam Tuivailala’s homer suppression.

With Yoshihisa Hirano, Matt Magill, Erik Swanson, Tuivailala, Carl Edwards Jr., and Brandon Brennan all appearing to be locks for the bullpen come Opening Day, it’s far from a guarantee that Grotz will be breaking camp with Seattle. Every bullpen needs a ground ball specialist, though, and even if he opens 2020 in Tacoma, it’s all but a guarantee that Grotz will see a fair amount of time in Seattle. If he keeps throwing that excellent splitter and figures out a way to get more whiffs from his other pitches, he could establish himself as a strong middle reliever: quite a journey from the humble beginnings of the 28th round and three years in indy ball.