Law's scouting notebook: Pirates' top prospect shows ace potential, but needs time

After pitching well for much of the season with the Bradenton Marauders, Pirates prospect Mitch Keller is getting his first taste of Double-A action with the Altoona Curve. Cliff Welch/Icon Sportswire

Pittsburgh's Mitch Keller ranks among the best pitching prospects in the minors right now, along with Michael Kopech (White Sox), Forrest Whitley (Astros), and Walker Buehler (Dodgers), and like Whitley, he was recently promoted to Double-A after dominating in A-ball.

Keller started for the Altoona Curve on Tuesday night against Hartford in the brand-new Dunkin Donuts Park, throwing five solid innings that showed why he's my No. 10 overall prospect but also why he's not going to race to the big leagues any time soon.