"We're running out of time, and the only way I can come back is if I'm at 100 percent," Gardner said. "Hopefully I get there, but we'll see. It all depends on how quickly I heal and how well I take care of it."
Gardner said that it would be at least a week before he could begin moving around, a timetable that manager Joe Girardi agreed with.
"I think you've got to give him a week to see where he's at," Girardi said. "I think he'll be a pinch-runner maybe before he can do anything else. He's a ways from picking up a bat."
Without Gardner, who batted .273 with eight homers, 52 RBIs and 24 stolen bases in 145 games, the Yankees have handed center-field duties back to Curtis Granderson.
"It's frustrating, but the team's still in this, and I'm happy I'm here to be with them and cheer them on," Gardner said. "I hope we play well the last couple weeks of the season, whether I'm in there or not."
Bryan Hoch is a reporter for MLB.com. Follow him on Twitter @bryanhoch and read his MLBlog, Bombers Beat. This story was not subject to the approval of Major League Baseball or its clubs.