Pittsburgh Pirates: JT Brubaker, Zach Thompson Emerging For Rotation

Pittsburgh Pirates right-handed starters JT Brubaker and Zach Thompson have become an underrated duo in the team’s starting rotation

The Pittsburgh Pirates starting rotation has been quite good this year. Dating back to May 1st, their five primary starters, Roansy Contreras, JT Brubaker, Jose Quintana, Mitch Keller, and Zach Thompson, have a combined 3.64 ERA, 4.04 FIP, and 1.36 WHIP. All told, that’s pretty good. Only Keller has an ERA over four in this time but has improved significantly since adding his sinker. Since his sinker became a significant part of his arsenal, Keller has a 3.78 ERA and 3.53 FIP.

But we’re not here to talk about Keller. Although Keller has done well recently, the two arms I want to focus on today deserve more love than they’ve been getting. That’s right-handers JT Brubaker and Zach Thompson.

Brubaker had plenty of questions to answer going into 2022. He was coming off a horrible 2021 campaign that saw him average over two home runs every nine innings. Although the underlying numbers supported a better pitcher, he’s even outperformed his 2021 ERA estimators, at least since mid-April.

After allowing ten earned runs in his first three starts, Brubaker completely turned things around. Since April 24th, Brubaker has tossed 81.2 innings, posting a quality 3.53 ERA, 3.49 FIP, and 1.38 WHIP. Brubaker’s walk and strikeout rates are roughly league average, coming in at 8.6% and 23.2%, respectively. However, the gopher ball, the main thing that killed Brubaker last year, has been a strength for him this year. He has just a 0.77 HR/9 throughout these last 15 outings. His 44.2% ground ball rate is slightly above average, which helps make up for his pretty unassuming exit velo and hard hit numbers.

What changed this year for Brubaker? Last year, he was a slider/sinker/fastball type pitcher. He used that trio of pitches at least 20% of the time, each with his slider being his most used offering. This year, however, he’s become a sinkerballer, using the pitch nearly 40% of the time (39.8%, to be exact). His slider and change-up usage rates have only changed marginally, but his four-seam fastball usage rate dropped from 24.5% to 7.6%. Although batters have a .334 wOBA against his slider, they have a .291 xwOBA against it, so Brubaker might not be done improving yet.

Zach Thompson was one of the newest additions to the Pittsburgh Pirates, being one of the three players acquired in the Jacob Stallings trade. The right-hander was a surprise rookie in 2021, posting a 3.24 ERA, 3.69 FIP, and 1.21 WHIP in 75 innings of work. Pretty good for a guy they signed the off-season prior to a minor league deal with an invite to spring training.

Like Brubaker, April was a rough month for Thompson. He allowed 16 earned runs in his first 14.1 innings of the season. So far, the earned runs in those 14.1 innings and four outings make up half of the total earned runs he’s given up this year. He’s surrendered just 16 more in his next 56 innings.

Since those first four outings, Thompson has a 2.41 ERA and 1.19 WHIP in his next 56 innings of work. But Thompson’s FIP stands at over 5.00. That’s not good, but a few factors cause it. One, he’s not a strikeout pitcher. Two, he isn’t a command pitcher either. Three, he’s given up his fair share of home runs.

But some more underlying numbers support Thompson’s case. He’s a ground ball pitcher. The right-hander has a ground ball rate of 47.9% since his fifth outing of 2022, the 29th best in baseball (min. 50 IP). Going into his start on Thursday, Thompson had an HR/FB ratio of 18%, the 12th highest among pitchers with 40 or more innings pitched since May 1st.

After his Thursday start, his HR/FB ratio decreased to 16.1%, but still high given the league-average rate is 11.5%. Given his roughly average hard hit and exit velo numbers and well above average ground ball rate, his HR/FB rate is fluky at best and unlucky at worst. His expected FIP, which helps normalize his HR/FB ratio, puts him at 4.45. That’s still not great, but much better than his actual FIP and an improvement over the 4.65 mark he had last season.

Both Brubaker and Thompson could be key parts of the Pirate rotation in the long haul. Thompson still has two years remaining before he even reaches arbitration, and Brubaker will be going into his first year of arbitration this off-season. They might not be super flashy names, but the important thing is they get the job done.