"It was a little nerve-wracking at first," Johnson said after the game. "I know we're in a pennant race. You see some of the younger guys come up [from Indianapolis], and you don't want to be that guy [who falters]. Same game. Bigger stage."
Michael McKenry was transferred from the 15- to the 60-day disabled list to open room on the 40-man roster for Johnson, while outfielder Andrew Lambo was optioned to Indianapolis to create a vacancy on the 25-man active roster.
The Bucs made the move with three members of their bullpen unavailable Sunday due to recent workloads.
Selected in the first round of the 2006 First-Year Player Draft by the Red Sox, Johnson becomes the latest former No. 1 Draft pick to land in Pittsburgh.
Signed by the Pirates as a Minor League free agent following the 2011 season, Johnson has remarkably reignited his career in the Bucs' system, combining for an 18-8 record and 2.75 ERA in nearly two full seasons with Double-A Altoona and Indianapolis. Significantly, in between he also had a fabulous Winter League season in the Dominican, posting a 1.06 ERA while allowing only 37 hits in 49 1/3 innings.
Johnson has spent this season mostly in Indianapolis' rotation, going 10-3 with a 2.18 ERA in 20 starts. He has made five relief appearances, none since June.
Right-handers Vin Mazzaro, Jeanmar Gomez and Bryan Morris were not available to pitch Sunday.
Since last Sunday, Morris in particular has been pressed, making four appearances and throwing a total of 99 pitches -- including 36 in working the final 1 2/3 innings of Saturday's 15-5 loss to Arizona.
"I certainly threw more pitches [Saturday] than I would've wanted to. It does wear on you, but that's how the season goes," said Morris, who had specifically told manager Clint Hurdle that he didn't want to sit out any of the recent series in St. Louis, in which he wound up throwing 46 pitches. "Those were important games, and when you're feeling good, you don't want to not pitch."
Tom Singer is a reporter for MLB.com and writes an MLBlog Change for a Nickel. He can also be found on Twitter @Tom_Singer. This story was not subject to the approval of Major League Baseball or its clubs.