When Brett Favre took the practice field for the Vikings today, he carried with him a throwing arm that has “a little rotator cuff tear,” his agent, Bus Cook, revealed on Tuesday.

“When he said recently that he would not play, he was not sure it would get worse,” Cook told NFL.com senior columnist Thomas George. “It was found on a follow-up MRI (to arthroscopic surgery he had on the arm in May). He feels like now the shoulder is not going to get any worse. He still feels like he can play at a high level with it. So, he’s back to play football. But he was not going to do it unless he felt he could give a day’s work for a day’s pay.”

Cook also told George that Favre’s decision to return with the Vikings had nothing to do with getting revenge on the Packers, as has been speculated by various media outlets. The Vikings and Packers play twice this season, in Week 4 at Minnesota on Monday Night football and in Week 8 at Lambeau Field.

“This is not about playing Green Bay,” Cook said. “Brett wants to win another Super Bowl. That’s what this is all about. He knows it is a long, hard road to do that. But winning the Super Bowl for him this season would be a crown jewel.”

George will have a complete column on the Favre saga later today on NFL.com.