The Potential Tools: 60 FB, 55 SL, 50 CH, 50 command

Strengths: Big, sturdy frame; clean, repeatable delivery; fastball works in middle 90s and holds velocity; downhill plane can show arm-side life in lower-velocity band; slider flashes plus; an out pitch in mid-to-high 80s with tight spin, dive and tilt; changeup will flash plus in low 80s with tumbling action; can show command within zone with all three pitches; natural feel for his overall arsenal.

Weaknesses: Lacks deception; pitches can flash higher than projections but are inconsistent; fastball can get straight when elevated; gets squared-up often; lacks fortitude; passive aggressive approach to pitching.

Role Ceiling: 55; #3 SP.

Risk: Moderate; still struggles to pitch with all three pitches on a consistent basis; reliever role could become more likely in near future.

Summary: Appel is one of the more interesting prospects in the minor leagues. On some nights, he can flash a frontline arsenal in one inning but then have evaluators quickly scratching their heads when it disappears the next. Coming to Philadelphia in the Ken Giles trade with Houston, he was arguably the player with the most upside in the deal. The most concerning thing about Appel is the passive-aggressive approach he has when pitching, but the change of scenery could pay dividends for him. If Appel can consistently harness his arsenal and pitch with aggressiveness on a night-in and night-out basis, he could overachieve his ceiling. But at this point, it’s more likely Appel becomes a reliever than a frontline starter.