Top prospect Mitch Keller will make his major-league debut Monday for the Pirates, a club source confirmed Saturday night.
The Pirates play the Reds in a day-night Memorial Day doubleheader at Cincinnati. It is not clear which game Keller will start.
Keller has gone 5-0 in nine starts with Class AAA Indianapolis this season. The 23-year-old has a 3.45 ERA and 1.42 WHIP along with 56 strikeouts and 20 walks in 47 innings.
The Pirates selected Keller in the second round of the 2014 amateur draft from Xavier High School in Cedar Rapids, Iowa. In six professional seasons, he has a 34-17 record, 3.52 ERA and 1.16 WHIP in 96 games.
The Pirates are missing injured Jameson Taillon and Trevor Williams from their rotation. They had used openers in three of their last six games prior to Saturday to try to fill the void.