What happened to Mo?

I know that it was just one game, and that Rivera will be fine, but that was ridiculous. A grand slam? That might be the 2nd-least likely thing that ever happened to Rivera, only to game 7 of the 2001 world series.

He only allowed 5 inherited runners to score all of '09, but yesterday allowed all 3 of the runners he inherited from Joba to score. He walked 1 batter. Yes, Rivera occasionally walks batters. But, in 5+ innings, Sergio Mitre only walked one batter. Rivera threw 14 pitches, with only 7 of them being strikes. None of his strikes were swinging strikes. Yesterday was only the 2nd time all year that Rivera had 0 swinging strikes in a relief appearance. The only other time Rivera did not have any swinging strikes was when he threw 4 pitches to get a 1-out save against the Angels on April 15th.Rivera just didn't have his good stuff.

So, we know how bad Rivera was yesterday. But, why? That's a pretty simple answer. Rivera had an 11 day layoff between appearances from April 30th (a save situation) to May 12th because of some pain in his side. His appearance on May 12th was in a non-save situation in an 8-0 game. His next appearance was on May 14th, another non-save situation in an 8-4 game. Then, there was yesterday's appearance. So, there were 15 days between save situations for Rivera. He was rusty. He got into a couple of games since coming back from the injury, but no save situations. He just wasn't prepared to come in to a bases loaded jam. The Yanks should have kept Joba in, and whatever happened would have happened. Maybe if Rivera came into the game in a save situation, but with no additional pressure of runners on base, he would have been okay. That being said, I agree with Girardi's decision to bring Mo in because he expected him to be his regular self. Rivera has come back from injuries before and immediately done well. For example, after having to sit out from September 1st to September 7th 2009 with a groin injury (Phil Hughes saved 2 games), he came back on the 7th and got a save that game and a win the next game.

Basically, Rivera just had a really bad game because of rust from not being in a save situation for over 2 weeks. He'll be fine next game.