Diehl was drafted by the Yankees in the 27th round of the 2016 draft. He posted ridiculous numbers in Advanced A before being promoted to Double-A in July. The lefty logged 75.1 innings in relief between the two stops, pitching to a 2.51 ERA with 108 strikeouts against just 23 walks.
Listed at 6-foot-2 and 180 pounds, Diehl has a lean and slender frame with room to add muscle. A short arm-action and crossfire landing hide the ball, playing up his low-90s fastball a tick. There’s only modest run on the heater, but he commands it well around the plate and throws a lot of strikes. Diehl’s only secondary pitch is a slider at 80-to-82 mph. He shows good feel to vary the shape and depth on the pitch, mixing a wider variant to expand the zone with two strikes. Both offerings are aided by his poised, aggressive mound presence and overall pitchability.
Diehl doesn’t have the raw stuff to profile in high-leverage innings, but he’s a fairly safe bet to fill a FV 40 situational role at the big league level. His angle and feel for the slider project to be a tough look for same-side hitters. He’s a low-risk, low-reward type prospect.