Last year, Pittsburgh Pirates’ pitching prospect Antwone Kelly had a massive and unexpected breakout. Heading into 2025, Kelly wasn’t ranked as a top 30 prospect in the Pirates’ system by MLB Pipeline or Baseball America. However, after putting up outstanding numbers in 2025, he has become one of the Pirates’ best prospects. Kelly now ranks as the Pirates’ 8th best prospect on Baseball America. Kelly’s 2025 breakout was nothing short of impressive. Now, what Pirates prospect might we see take an unexpected meteoric rise in 2026? The Pirates have no shortage of candidates.
Alessandro Ercolani
Alessandro Ercolani was signed the same offseason the Pirates signed Kelly. Ercolani hails from the small of San Marino. Last year, Ercolani pitched at Double-A in just his age-21 season. His 4.04 ERA and 1.23 WHIP looks solid, but his peripherals were rather poor. He only struck out 15.7% of opponents, with a 9% walk rate. Ercolani had a 4.92 FIP and 5.29 xFIP.
While his bottom line numbers may not have been great, there’s certainly reasons to believe that Ercolani is in for a big 2026. Last year, he was among the top 150 minor league pitchers in Stuff+ at 113. He also had a 113 normalized Stuff+, which adjusts for different types of pitches. His Stuff+ was even above Kelly, who came in at 108.
Ercolani stands at 6’4”, 185-LBS. While he sits in the lower-90s right now, an uptick in velocity isn’t unprecedented. He can hit the mid-to-upper-90s, and is still young enough he may find another gear. 2026 will only be his age-22 season, one year older than Kelly when he broke out, and Ercolani already spent an entire year at Double-A. While Ercolani ranked as the Pirates’ 21st best prospect going into 2025 by Baseball America, he isn’t on any top 30 Pirates prospect list as of right now.
Jeter Martinez
Jeter Martinez is among the Pirates’ top 30 prospects, but it’s not for his performance. Acquired at the 2025 trade deadline from the Seattle Mariners for Caleb Ferguson, Martinez put up a 7.06 ERA, 4.37 FIP, and 1.72 WHIP over 75.2 innings of work at the A-Ball level. A .361 batting average on balls in play indicated some bad luck played a hand in his performance, but it didn’t excuse the 13.7% walk rate, 21.6% K%, or the meager 7.8% K-BB%. On the plus side, he induced ground balls at a 49.7% clip, and only allowed a single home run all year.
Martinez already sits mid-90s with both his two-seam and four-seam fastball. His mid-80s slider is another potential above-average offering. The right-hander will also toss a change-up. This pitch has good movement, but he struggles to find consistency with it. While he has an impressive pitch mix, his control is his biggest downside right now.
However, Martinez was only in his age-19 season last year. He was the eighth youngest pitcher at A-Ball to make 15+ starts. Prior to his breakout, Kelly also had a mediocre 11.3% walk rate and 10.3% K-BB% at the same level in 2024. Martinez just turned 20 earlier this February. The Pirates have worked hard with Martinez to improve his delivery, which should hopefully help him land more strikes and find a consistent feel for his pitch mix.
Zander Mueth
Zander Mueth was the Pirates’ second round competitive balance pick in 2023. The right-hander was one of the more intriguing prep pitchers of the class. Mueth has tossed 100 innings as a professional, logging a 3.42 ERA. He has also allowed just three home runs and has struck out 27.2% of the batters he has faced. However, control has been an issue for Mueth. His career walk rate clocks in at 16.9%.
Mueth throws both a four-seam and two-seam fastball that sit around 94-95 MPH, topping out at 98. His mid-80s slider has induced a whiff rate of nearly 40%. The right-hander will also mix a change-up and cutter into his pitch usage. Mueth throws from a low arm slot, with above-average extension off the mound. That makes his already above-average stuff play up to another level.
The control is obviously a question mark, but that’s the same story for Kelly at this time last year. Mueth is also still young, as he won’t turn 21 until late June. Mueth’s stock has dropped, as he is only ranked as the Pirates’ 25th best prospect on Baseball America, and isn’t even top 35 on FanGraphs’ top Pirates prospects. However, he was a top 60 draft prospect just a few years ago. Expectations may be low for him after walking 21.5% of opponents and only pitching 26 innings last year, but that only makes a breakout more unexpected, just like Kelly last year.
