Hirsh, 27, has not pitched in the Major Leagues this season. He was 6-7 with a 6.66 ERA in 20 games (16 starts) for Triple-A Colorado Springs of the Pacific Coast League. In 101 1/3 innings, Hirsh allowed 130 hits and 78 runs (75 earned) while walking 35 and striking out 59.
The righty started 19 games for the Rockies in 2007 when they advanced to the World Series, but he appeared in only four games (one start) last season at the big league level.
Yankees general manager Brian Cashman has been in the market for pitching depth. New York has had to dip into its Triple-A reserves this season, most recently promoting Sergio Mitre from Scranton/Wilkes-Barre to replace Chien-Ming Wang, who is out for the season, in the starting rotation.
"I don't think you can ever have too many innings, and you've got to be prepared if something happens," Yankees manager Joe Girardi said. "Right now, our rotation is throwing the ball very well. But this time of year, I don't think you can ever be too careful."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.