Joe Girardi seemed to pour some cold water on the idea that Mariano Rivera could possibly return from knee surgery to pitch again this season.

In an interview with Michael Kay of ESPN New York 98.7 FM on Monday, Rivera said it was "my goal'' to make it back this season from surgery to repair a torn ACL.

"I don't think about it because if it doesn't happen, I will be kind of like disappointed,'' Rivera said. "I take it day by day. I'm working hard and doing what I do. ... That's the way I'm thinking, day by day and positive, definitely. Optimism, positive. Whatever the Lord will allow to happen, will happen."

Girardi wouldn't say a Mo comeback this season was impossible, but admitted, "It's going to be very difficult.''

Rivera underwent surgery on June 13, nearly six weeks after suffering the injury on while shagging flies during batting practice on May 3 in Kansas City.

"I know he kinda left it open,'' Girardi said. "He didn’t say he was definitely gonna make it back. He’s trying. My anticipation it’s going to be very difficult because it’s a short period of time but let’s see what happens.''

Girardi said Rivera would need a spring training-like period, which for him generally means six to eight innings of pitching spread over a three-week period, before he could return to the majors. That means Rivera would have to be fully recovered and ready to begin a minor-league rehab assignment by the first week of September to have any hope of getting into a regular-season game before the playoffs begin in the first week of October.

"I don’t know if it's possible,'' Girardi said. "It’s really tough because there’s not a lot of minor-league baseball in September.''