When the Rockies signed Prosecky for a just over $300,000 bonus after drafting him in the sixth round in 2022, most observers thought the left-handed pitcher would be ticketed to the bullpen. After all, that’s where the 6’3″ pitcher had distinguished himself in college as Louisville’s closer. Instead, the now 24-year-old moved into the starting rotation in his first full professional season and has remained there ever since. As a prospect, Prosecky combines a deceptive fastball in the low-to-mid 90s with a curveball, slider and change-up with a high spin rate.
After a strong 2023 spent in Low-A Fresno, Prosecky’s 2024 season was postponed by elbow inflammation until mid-June, limiting him to 48 2/3 innings over 14 games for a combination of the ACL team, Low-A and High-A. The good news was that he struck out a whopping 14.4 batters per nine innings, albeit against younger competition. Prosecky also received a farewell party in the Arizona Fall League, where he threw another 15 1⁄3 innings with poor run suppression numbers (7.63 ERA, 2.02 WHIP and 5.3 BB/9 rate) and strong strikeout numbers (13.5 K/9 rate). All told, across 22 appearances in four leagues in 2024, Prosecky finished with 101 strikeouts in 64 innings pitched (14.2 K/9 rate), 30 walks (4.2 BB/9 rate) and 37 earned runs allowed (5.20 ERA).
In 2025, Prosecky returned to High-A Spokane, where he was 0.8 years older than the league average. He stayed healthy, throwing 88 2/3 frames of 3.86 ERA ball in 18 starts with a 1.26 WHIP, 9.4 K/9 rate and 4.2 BB/9 rate. That’s a significant K/9 drop, but the run prevention numbers have improved enough to earn Prosecky a post All-Star break promotion to Double-A Hartford, where he was 0.7 years younger than the league average. In nine starts with Hartford, Prosecky posted a 4.97 ERA (4.81 xFIP) in 38 innings, built on his 1.55 WHIP, 8.1 K/9 rate and 5.4 BB/9 rate. Overall, it was nice to see Prosecky have success against the upper minors battle.
Here’s Prosecky striking out 10 in a start for Spokane last year:
The 6-foot-1 southpaw has the size and repertoire to potentially start, with a four-pitch mix. At his best, he runs his fastball at 90-90 mph and drives it well, missing bats along the way. He has a late-action slider with depth, a slower curve that he can use to steal a shot and also a better feel for his changeup.
Prosecky had thrown just 64 innings in college before reaching the top 100 IP in 2023. The Rockies are hopeful that a now fully healthy Prosecky, who has generally been in the zone when he’s at his best, can hit the reset switch and start moving back up the ladder in 2025.
Prosecky is only sitting at 91-93 mph, but hitters don’t seem to be picking it up. The southpaw has a short, vertical arm stroke that allows his heater to play like a bat miss in the zone despite having below-average speed. He hides the ball forever and he seems to jump on hitters very quickly. He throws a classic 12-to-6 curveball off of that, a pitch that’s virtually indistinguishable from his fastball until it starts to curve with tremendous, bat-missing depth. These two pitches give Prosecky a reliever base with lower leverage. Prosecky’s arm strike isn’t always well-timed, and his results throwing the strike were mixed during this effort as a starter. In the 2024 Fall League, Prosecky worked a second breaking ball, a slider in the 80-80 mph range that looked below average. There’s certainly more variety here than is typical for someone who is 92 years old, but Prosecky follows as a low-leverage southpaw.
Prosecky fails to fire the radar gun, but gets by thanks to a heater from the 90s. With a four-pitch mix, Prosecky has more of a typical starter repertoire. What he misses are reps, as a reliever in college who subsequently missed time due to injury. Colorado sent him to the Arizona Fall League, where he continued to miss bats but also put up runs in an environment friendlier to older hitters. A full health season would see Prosecky finish next year after spending a fair amount of time in Hartford and continuing to miss bats. His floor is elevated as a bullpen piece, but as long as he appears startable, he’s accomplished enough to earn the looks.
Prosecky was my sleeper for the Rockies last year, but after going to an outside lab to try to increase his speed, he developed elbow inflammation and never got back on track. He threw a total of 63 innings between the regular season and the Arizona Fall League, with terrible results in the fall and in High A. Even when he pitched, he was 90-94, down from 92-95 the year before; he barely used his slider; and his command was far off. When healthy, he has a four-pitch mix, with the slider being his best offering and a changeup that could flash plus but didn’t stay there. There is guile in his delivery to help play the fastball as well, as long as he locates it. Let’s hope a complete offseason rest gets him back to his 2023 form, when he looked like he could be a mid-rotation starter.
It’s interesting to see the difference in evaluation of the curveball: for Law and MLB Pipeline, this is Prosecky’s weakest pitch, but for Longenhagen, this is his best.
Prosecky has been a pleasant player development surprise for the Rockies thanks to his jump in the value spectrum of the pitcher role and his effectiveness in the role. He missed fewer bats in 2025, but took a step forward in run prevention at the next level while pitching 126 2/3 innings. The Rockies didn’t protect Prosecky from the Rule 5 Draft this season, but he wasn’t selected, so he’ll likely return to Hartford to start in 2026 and be a big-league rotation option later in the season. I placed Prosecky in the middle of my 35+ FV level, 29th on my list.
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