Rivera entered a tie game in the ninth inning Thursday and gave up back-to-back home runs for the first time in his sensational 15-year career, as the Yankees dropped their fifth in a row with an 8-6 loss to the Rays.

"It's tough when I come into situations like tonight and don't do my job," Rivera said. "It's just unacceptable."

The news got worse after the game, when Joe Girardi admitted Rivera, 39, has been slow to recover from offseason shoulder surgery and that the club was hoping the six days off he had from April 30-May 5 would help him regain his form.

"The velocity is not there where it was last year ... I still think he's coming back from the surgery he went through, and that's why we've been very careful with him," Girardi said. "He feels good now, which is good, but last week he had some issues and we had to be careful with him. There's nothing serious, it's just the strength coming back and coming back from the injury that he had. And we're trying to be smart with him."

Rivera was impressive Wednesday, when he allowed one hit and struck out the side in a tie game in the ninth inning. But he looked nothing like the Rivera of old in giving up the back-to-back homers by Carl Crawford -- who hadn't gone deep since last June 27 -- and Evan Longoria.

Rivera, who has given up as many home runs in 11 1/3 innings this year (four) as he did in 70 2/3 innings last year, said his struggles were not related to his diminished velocity and that he expects to feel stronger as the season goes on.

"I don't think it's 100 percent, but that's no excuse, that's not the reason why I lost the game today," Rivera said. "I feel great. The strength, it will be there. That's not my concern at all."

Longtime teammate Andy Pettitte -- who set an ignoble career milestone as well Thursday by giving up four homers in a start for the first time -- expressed similar sentiments and said he's not worried about Rivera.

"Unless he's hurt, I don't have any concerns," Pettitte said. "I think he's throwing the ball great, he punched out the side (Wednesday) night when he came in. I don't think there's a whole lot to worry about."

Time will tell if Rivera and Pettitte are merely optimistic or in denial.

RAYS 8, YANKEES 6: Mariano Rivera gave up back-to-back homers to Carl Crawford and Evan Longoria in the ninth inning -- the first time he's ever surrendered back-to-back blasts -- as the Rays broke a tie and handed the Yankees their fifth consecutive loss. Johnny Damon went 4-for-5 with a homer and four RBIs while Hideki Matsui had a solo homer, and Jose Molina added an RBI. Andy Pettitte labored through six innings, during which he gave up five runs on nine hits, including a career-high four homers.