The Pirates optioned Holmes to Triple-A Indianapolis on Monday, Adam Berry of MLB.com reports.
Holmes was recalled from Indianapolis to offer the Pirates some length out of the bullpen for the team's doubleheader Sunday against the Tigers, but he ended up going unused in both halves of the twin bill. He'll now resume preparation for a starting role with Indianapolis this season after going 10-5 with a 3.36 ERA and 1.38 WHIP across 112.2 innings with the Triple-A club in 2017.