Pittsburgh selected Nicolas' contract from Triple-A Indianapolis on Tuesday.
The 24-year-old will get his first taste of major-league action down the stretch after posting a 5.20 ERA and 127:52 K:BB in 98.2 innings this summer between Double-A and Triple-A. He showed much better following a move to the Indianapolis bullpen in early August, delivering a 2.05 ERA with 31 strikeouts across his last 22 frames. Thomas Hatch was optioned out in a corresponding 28-man roster move.