Vikings coach Leslie Frazier said Monday that an MRI on Brett Favre's injured throwing (right) shoulder today confirmed he has a sprained sternoclavicular joint. Frazier said a decision will be up to Favre and the team's medical staff.

"If the doctor says he's fine, he's functional and Brett feels good about it it won't be a hard decision," Frazier said. "Between what the medical people tell me and what Brett tells me we'll make a decision based on that."

Frazier said rest would be the key and that surgery isn't needed on Favre's shoulder. Frazier did say he's confident Favre will be honest about how he feels as the week goes on that and that the fact Favre admitted he could not return Sunday proves that to be the case.

Favre was hurt Sunday on only the third play from scrimmage and did not return. Favre admitted he could have not have thrown the football after that. Favre said following the game that he was not overly concerned about the injury, but one has to admit that when a quarterback says he can't throw the football that is never a good thing.

Frazier made it clear after the victory over the Bills that if Favre is healthy he will be the starting quarterback on Sunday against the New York Giants at Mall of America Field. Favre, 41, already holds the NFL record for consecutive starts and Sunday would be his 298th.

Frazier admitted he was surprised that Favre did not return Sunday. "I thought he would come back in the game," Frazier said. "As hard as I saw him get hit, I've seen him take harder hits. Nobody is tougher than Brett Favre. I was surprised he wasn't able to make it back."

Frazier, meanwhile, confirmed the Vikings have signed free agent running back Lorenzo Booker, who has been in the UFL.