Colin Selby may have been the most surprising player among Pirate minor league arms last season. A late-round selection out of a D3 college, Selby never appeared to be more than organizational depth. But he made some major improvements in 2022 and even earned a 40-man roster spot. Selby owned a 2.27 ERA, 2.92 FIP, and 1.21 WHIP through 35.2 innings. Selby struck out nearly 30% of the opponents he faced (28.9%) with an outstanding 0.50 HR/9 rate. The right-hander had a ground ball rate above 50%, which is one of the reasons he prevented home runs as well as he did.
Selby's weakest number was his walk rate. He had a 9.4% walk rate, which is still a more than a manageable number. Selby throws a high-90s fastball with a plus slider and curveball. Selby definitely has the potential to become a high-leverage reliever sometime next year. He, along with Yerry De Los Santos, Colin Holderman, and David Bednar, could form an extremely underrated back-of-the-bullpen quintuple.
Tahnaj Thomas had a fantastic summer last year, rebounding from an awful 2021 and reinventing himself as a reliever. From June through September, the flamethrower managed a 1.98 ERA, 2.70 FIP, and 1.05 WHIP. Thomas has always been a great strikeout pitcher and had a 28.5% K-rate, but walks have consistently been an issue. However, during this stretch, he cut his BB% down to just 6.9%. On top of that, he had a .5 HR/9 rate.
Thomas has a fastball that can hit triple digits. Along with that, his slider is above average. Though his change-up is rarely used, and when he has used it, it's well below average. That has always been the sticking point for Thomas, as he's consistently been a two-pitch pitcher. But after being put into a position where he could take advantage of his strengths and adjust to his new role, Thomas went on a hot streak and put up great numbers.
J.C. Flowers is certainly one of the more interesting names in the Pirates' system. An outfielder during college, the fourth-round pick is still fairly new to pitching. Nevertheless, he has some very good stuff on the mound to go with plus-plus athleticism. Flowers also didn't get off to a great start, but by June, he was fully settled in. His final 38 innings saw him post a 2.61 ERA, 3.31 FIP, and 1.03 WHIP. Batters struggled to get hits off of Flowers, holding them to a .184 average against. Plus, he had a 27.3% strikeout rate, a 9.1% walk rate, and a .47 HR/9.
The outfielder-turned-pitcher can hit the upper-90s with his fastball and typically sits in the 94-96 MPH range. However, his slider is the real weapon. It's one of the best in the minor leagues. He also throws a two-seamer and a change-up with average potential. Flowers pitched multiple innings in most of his outings and made two starts all season. The pitch mix and athleticism give him a brighter outlook than most relief prospects. It would be nice to see him receive a larger workload and become a starter. Flowers does have the excuse of not having much experience under his belt. He has 203.1 innings between college and professional levels.
Undrafted free agents typically aren't considered to be among your top prospects, but Nick Dombkowski will certainly get a chance to prove himself next season. Dombkowski played at three levels of the minor leagues, starting the season at Bradenton and ending the year at Altoona. All told, he pitched 67.1 innings, working to a 3.06 ERA, 3.26 FIP, and 1.10 WHIP. Dombkowksi had the best strikeout rate among Pirate minor league relievers at 30.7% but also had a healthy 6.8% walk rate and 0.94 HR/9.
Despite the number of strikeouts he induced, Dombkowski only works in the 88-91 MPH range. But he throws a slider with above-average spin and a change-up with decent movement. His best tool is his ability to locate, which helps his stuff play up. Dombkowski worked in a swing-man role, making 36 total appearances and two starts. He might not be a high-leverage guy, but there's definitely value in a pitcher who can go two innings at a time.
Another left-handed reliever of note is Tyler Samaniego. A 14th-round draft pick, Samaniego is coming off a season in which he had a 2.46 ERA, 3.45 FIP, and .80 WHIP. Samaneigo struck out just over a quarter of opponents with a 25.5% strikeout rate and allowed just two home runs in 47.2 innings. The southpaw's ground ball rate of 57% was the seventh best among Pirate minor league arms with 30+ innings pitched.
There were a few worrying factors about his season, though. While the lefty decreased his walk rate from 16.2% to 7.8% after moving from Greensboro to Altoona, his strikeout rate plummeted from 35.3% to just 19.8%. He also had a .142 batting average on balls in play. Granted, he was a heavy ground ball pitcher, but that is still extremely low. But Samaniego definitely could carve out a role in the Pirates' bullpen. If either Jarlín García or Jose Hernandez struggles, then you might see Samaniego take over their role.
Cody Bolton had a solid rebound campaign. Although there were a few red flags, he could become a solid swingman-like pitcher. After missing two years of playing time, Bolton had a 3.09 ERA, 3.81 FIP, and 1.28 WHIP. He struck out just over a quarter of the batters he faced with a 25.4% strikeout rate while only allowing four home runs in 75.2 innings. But the red flags were that he had a 12.4% walk rate and an HR/FB ratio of 5.1%, making his HR/9 rate's sustainability questionable.
He mostly worked in a swing-man role, with 14 starts across 30 appearances. Bolton has never been a flamethrower and sits in the 91-94 MPH range. Nevertheless, his fastball, slider, and changeup are all average to slightly above-average offerings. Bolton will turn 25 in Mid/late June. In the event of an injury, he might be one of the first guys promoted.