"With Masa coming off the DL on Wednesday, and [Ivan] Nova not far behind, I figured it was a numbers game," Capuano said. "I'm going to try to be ready to do my job in the bullpen."
Warren hurled seven innings of two-run, six-hit ball in a losing effort against the Athletics on Sunday in Oakland, a 3-0 Yankees defeat. He is 3-4 with a 3.75 ERA in 10 starts this season, and over the last four starts, Warren has permitted eight earned runs in 26 2/3 innings (2.70 ERA).
"I think I've just been more aggressive," Warren said. "Trusting my stuff a little bit more. I think I'm getting in good counts, for the most part, and I'm a much better pitcher when I'm aggressive like that and using all four of my pitches."
Girardi said that he was not tempted to send Warren to the bullpen as a replacement for struggling right-handers David Carpenter and Esmil Rogers.
"Obviously, I think he could be really effective in the bullpen, but his starts are important, too," Girardi said.
Capuano lost all three of his starts, posting a 6.39 ERA since returning from the disabled list. Girardi said that he could use Capuano -- who made 28 appearances out of the bullpen for the Red Sox last season -- as a long reliever or in shorter stints.
"He's done both," Girardi said. "With Esmil, that can give you some distance. There might be a day when you could use him just as a long man."
The Yankees must make a roster move on Wednesday to clear a spot on the 25-man roster. It appears likely that one of the Yanks' four left-handed relievers will be trimmed, but Girardi said that he did not want to go into that thinking yet.
"We'll make that decision Wednesday. There's a lot that can happen between now and Wednesday," Girardi said.
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch, on Facebook and read his MLBlog, Bombers Beat. This story was not subject to the approval of Major League Baseball or its clubs.