Holmes was optioned to Triple-A Indianapolis on Sunday.
As expected, Holmes will head back to the International League after serving as the Pirates' 26th man during the big club's doubleheader with the Brewers on Saturday. Holmes started the second game of the twin bill and picked up his first big-league win, spinning six shutout innings while fanning six. He'll likely be at the top of the list for a promotion the next time the Pirates require a spot starter.