McGrath admits his axing for last night's game against Real Madrid was "remarkable".
“It’s remarkable,” he told talkSPORT. “I’m loathed to question Sir Alex Ferguson’s reasoning because he’s done so much in the game, but I don’t understand it.
“If you see Wayne Rooney’s name on the team-sheet you know you’ve got to be on your game because he can score from anywhere.
“He hasn’t been at his best this season but you saw what he can do in the dying stages against Norwich.
“That would have frightened Real Madrid more than seeing Danny Welbeck’s name on the team-sheet. It’s a strange one for me, I think Wayne’s future is up in the air at the moment.”