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Is JT Brubaker the Pirates’ staff ace?

Brubaker has been excellent for the Buccos. Is it time to start calling him an ace?

MLB: St. Louis Cardinals at Pittsburgh Pirates Charles LeClaire-USA TODAY Sports

To this point in the 2021 Major League Baseball season, the Pittsburgh Pirates have experienced highs and lows. We saw the club begin the season by going 1-6 before going 11-5 over their next 16 games and performing as one of the top teams in the National League. After that, the Pirates mostly came crashing back down to earth, now going 3-9 over their last 12.

This season, however, as we know, isn’t dedicated to winning baseball games, necessarily. Sure, that can be a fun byproduct at times throughout a 162-game marathon of baseball games, but we knew coming into the season that 2021 is a bridge year — just as 2022, 2023, and probably 2024 will be. For that reason, we’re looking for nuggets to grasp onto, mostly focusing on which players are worth keeping, which players are worth trading, and who might be around in the future.

While the Pirates’ bullpen was the talk of the town over the team’s period of April winning, boasting an eighth-best 3.57 ERA over that time, in addition to a fifth-best 3.34 SIERA, it was a starting pitcher who steadily amassed quality innings. Enter: JT Brubaker.

The 27-year-old Brubaker is making the most of his appearances in a subpar starting rotation. Drafted by the Pirates in the sixth round during the 2015 MLB June Amateur Draft out of the University of Akron, Brubaker steadily climbed through the organization’s ranks — and was named the organization’s Minor League Pitcher of the Year in 2018 — culminating in a 2020 major league debut.

During his first taste of baseball at the highest level, Brubaker started nine games (appearing in 11 games total), producing a 4.94 ERA, 112 ERA-, and 4.28 SIERA. But this season, the Pirates have gotten completely different production from Brubaker. Having more time to settle into a normal day-to-day routine, Brubaker has been excellent.

The Pirates seemingly de facto ace has been garnering more national attention as of late, even prompting Pitcher List’s Nick Pollack (@PitcherList) to “memeify” the Pittsburgh pitcher:

So, like Pollack, we’re all left wondering: Is this an ace? Let’s have a look and try to figure it out. To this point in the season, Brubaker has very obviously been the best starting pitcher the Pirates have to offer. With many names presumably ready to be moved as a moment’s notice, Brubaker gives the Pirates something to think about.

While there are some players you can guarantee won’t be around by the time the Pirates are ready to compete once again (probably in 2025), Brubaker’s in a tough spot. At age 27, by the time winning baseball has a shot to return to Pittsburgh, he’ll be in his age 31 season.

Unless he remains affordable — ahem, cheap — the Pirates don’t dole out money to talented players ready for a payday. This is largely contingent on when the Pirates are competitive. If it’s 2026 or later, forget about Brubaker being around. Furthermore, by the time the Pirates are ready to compete, will Brubaker be in a regression? Before those questions can be answered, we must first understand: is Brubaker really this good?

To start, Brubaker currently holds a 2.58 ERA. Among starting pitchers with at least 20 innings under their belt this season, that number is 27th best in baseball. Put another way: Brubaker would be the best starter by ERA on about 12 other teams in baseball.

His other numbers also seem to suggest that he’s emerging as a competent pitcher: for example, his 3.33 SIERA is also good for 27th in baseball, while his 66 ERA- is 26th. Finally, his CSW% (called strikes + whiffs / total pitches) is at 31.1 percent, or 44th best among starters. One way you could assess these numbers is by assuming that Brubaker is approximately the 31st-best starter in Major League Baseball (if all those numbers are weighted equally).

That’s pretty high praise. How’s he doing it?

Brubaker works predominantly with the slider, throwing it around 35 percent of the time, with his sinker being deployed around a quarter of the time. His fastball sees nearly the same amount of usage as the sinker (23.4 percent), while curveball (8.6 percent) and changeup (7.5 percent) lag quite a bit behind.

Brubaker seeks to work predominantly low and away from right-handed hitters (low and in to lefties). What’s interesting about Brubaker’s focus on the slider is its subpar movement, which moves approximately one inch horizontally and approximately 33 inches vertically. Nevertheless, Brubaker has built a heavy reliance on the slider. With his slider, Brubaker is producing whiffs at a rate of 37.6 percent.

His slider works as a “put away” pitch around 34 percent of the time, produces a strikeout percentage of nearly 36 percent, and an xBA of .237.

While many of Brubaker’s numbers are “good,” they haven’t struck me as ace numbers. If a pitcher’s primary pitch can’t mow down hitters, as it appears is the case for Brubaker, then that pitcher must be working well in tandem with a secondary pitch. So we turn to his sinker.

It’s with the sinker that Brubaker sees a lot of success in terms of run value. While Brubaker’s primary pitch, the slider, saw a run value of zero, his sinker holds a run value of -4, which is 11th best for that pitch among qualified pitchers.

It’s been a high value pitch for Brubaker in managing innings, despite its high xwOBA (.340). Brubaker will throw it pretty much all over the zone, but he will often throw it inside to right-handed batters; to left-handed batters, Brubaker will throw the pitch with glove side movement which has the ability to stay inside before jumping over the plate at the end of the pitch’s life.

But because Brubaker doesn’t have a ton of movement on his pitches, we must look to location. Gone are the days of location artists, right? At least, that’s what we’ve been told. If you listen to any old-timer broadcasters lamenting the state of the game, they’ll tell you it’s all about power pitching — in many ways, it is — and that nobody has any interest in watching somebody like Greg Maddux try to pitch. That’s simply not true.

While I’m not comparing Brubaker to Maddux, my point is this: every good pitcher you take, whether a fireballer or not, is good at commanding the strike zone. There’s a difference between a pitcher who throws hard for the sake of throwing hard and a pitcher who can command the ball and happens to throw hard.

Take a look (above) at every pitch Brubaker has thrown to right-handed batters this season. He clearly has a plan of attack and where he wants to go with his pitches, and that’s why he’s seeing success. Brubaker likes to predominantly work low and away from righty batters to induce weak contact. He doesn’t have some of the swing-and-miss stuff that other pitchers around the league have, so he has to make it work.

If you look at Brubaker’s spread against lefties, you’ll see a similar story. There’s a plan of attack where he wants to use that glove side sinker to cross back over the plate, pound the hitter inside with a slider, or drop a changeup that runs away arm side from the hitter on the outer third of the zone.

In the same vein as command, Brubaker’s 5.6 percent walk rate is 21st-best in baseball. Lastly, although Brubaker’s stuff doesn’t have the wicked movement we might expect from a chase king, he’s in the 84th percentile in chase rate, according to Baseball Savant.

Brubaker’s mixing of pitches and finding spots inside the zone — or outside of the zone — that he wants has been instrumental in his success. Don’t expect Brubaker to be an overpowering pitcher, and don’t expect him to lead the league in strikeouts, though he will have his fair share. Like pitchers we’ve seen in the past with the Pirates, Brubaker will rely on location and weak contact to continue to have success. As long as he’s inducing chases and getting batters to weakly hit balls (he’s in the 80th percentile in average exit velocity), then it seems perfectly reasonable to expect Brubaker to see continued success.

To conclude, it’s not apparent that Brubaker has the stuff to become an ace, but he’s certainly trending in a favorable direction. It’s worth noting that Brubaker becomes an unrestricted free agent in 2026, his age 32 season. He’s up for arbitration in 2023. What the Pirates do with him from this point on is anybody’s guess. It seems perfectly plausible that either of the two scenarios play out: he hangs around and becomes a key component in the Pittsburgh starting rotation once quality baseball returns to PNC Park, or he becomes another trade piece down the road before the Pirates are able to reach some sort of pinnacle again.