Girardi cited Aceves' four-pitch repertoire and success starting games last season as justification for choosing him over -- among others -- Sergio Mitre, who has been producing gaudy numbers for Triple-A Scranton.
Aceves last appeared in a game Sunday, throwing 43 pitches over four innings. He has thrown at least 33 pitches in four of his past five outings and will be on a pitch count of 65 on Thursday.
"We feel that out of the options, he's the most stretched out for us," Girardi said.
The need for a spot starter arose last week, when the Yankees placed Chien-Ming Wang on the disabled list with a right shoulder strain. Had the injury occurred a month earlier, the Yankees likely would have asked Phil Hughes to take his place. But Hughes no longer has the sufficient stamina to fill a starting role, and -- more importantly -- has become too much of a cog in the late innings.
"He's been dynamite in the back end of our bullpen," Girardi said.
The other option, Mitre, has produced a 3.26 ERA in five Triple-A starts, catching Girardi's eye by striking out 23 batters and walking just three. A veteran of the Cubs and Marlins, Mitre also boasts far more big league experience than Aceves and could have given the Yankees far more length.
But Aceves has ranked among the most successful Yankees pitchers of the past three months, forcing the team to consider him for the rotation. In four starts down the stretch last season, Aceves went 1-0 with a 2.74 ERA.
"I've been a starter for six years," he said. "This is what I want. I want to start, and I think we can do a good job."
If history is any guide, he will. But to move Aceves into the rotation -- either temporarily or for the foreseeable future -- is to take a calculated risk. Using Aceves for 65 pitches will force the Yankees to turn to long relievers Brett Tomko and Jonathan Albaladejo early in Thursday's game.
Even more constraining is the fact that the Yankees will lose one of their top bullpen arms. Aceves has spent the last three months developing into one of Girardi's most reliable relievers, pitching in as a long man, a setup man and everything in between.
"It was great having Ace down there," Girardi said of the bullpen. "I loved having him down there, because he served so many purposes down there for you. But we're in a little bit of a pinch, and we need a starter on Thursday, and we're going to put him there."
Whether Aceves will remain in that role after the All-Star break remains to be seen. But if Wang is out for an extended period of time, then Aceves could play his way into that role with a strong outing Thursday against the Twins.
"I haven't been trying to be a starter," Aceves said. "It's not in my hands, the decision. The only thing that I've tried to do is pitch the best way that I can, and that's it."
Anthony DiComo is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.