Currently, the Pittsburgh Pirates best pitching prospect is right hander Mitch Keller. He is currently a consensus top 50 prospect across the MLB, and has previously touched the top 20 in terms of rankings. It’s very arguable that Keller should still be in the top 20-30 top prospects.
Keller was an ace with the Triple-A Indianapolis Indians last season. He posted a 3.56 ERA, 3.60 FIP, and 1.24 WHIP across 103.2 innings. He struck out 123 batters, and walked just 35, which resulted in a strong 3.51 K/BB ratio. Even though nearly 40% of all batters with at least 300 plate appearances at Triple-A having an isolated slugging percentage of .