Keller was recently promoted to Double-A Altoona and will debut with his new team Sunday, Mike Rosenbaum of MLB.com reports.
Keller earned the move up the organizational ladder by delivering a 2.99 ERA and 0.98 WHIP on the season for High-A Bradenton, and he really turned up the production in his last three starts, going 2-0 with a 1.42 ERA and 14:2 K:BB. As the top pitching prospect in the Pirates organization, he'll be a name worth keeping an eye on for a potential move to the big club at some point in 2018.