The Pirates recalled Bolton from Triple-A Indianapolis on Sunday.
He'll give Pittsburgh a fresh arm out of the bullpen after the Pirates needed four relievers to cover the final six innings of Saturday's 5-0 loss after starter Vince Velasquez recorded just six outs before departing with right elbow discomfort. The Pirates placed Velasquez on the 15-day injured list to create room on the 26-man active roster for Bolton, who gave up three earned runs and struck out five in six innings across his prior three appearances out of the big-league bullpen this season.
