The Pirates will option Phil Irwin back to the minors without him appearing in a game. That's a shame for Irwin, who was hoping to make only his second big-league appearance and his first in over a year, but at least he gets a couple days of big-league money.
For the Pirates, it's nice that Irwin didn't have to appear in a game. It's not that he would have done badly, necessarily, but he was in Pittsburgh because of the extra-inning debacle the other night. Since then, though, pretty much the entire bullpen has been spared with Charlie Morton and then Gerrit Cole going eight innings apiece in the past two days.
The Pirates haven't announced who will be coming up, but it will probably be a hitter -- Francisco Liriano and Edinson Volquez are slated to pitch the next two games, so there's no need in the rotation, and the bullpen is almost completely fresh. As bearandpizza pointed out in the comments, Andrew Lambo would have been the obvious choice, but he's on the disabled list.