The one consolation for United was Nani's 69-minute outing on his return from a dislocated collarbone, although Ferguson admitted the player was off the pace after the break.
"Maybe we should have taken him off at half-time because we did get anything from him in the second half," he said. "Sometimes it goes that way when a player has been out for a while.
"He has only had seven days' training, so maybe we should have taken him off at half-time. It is good to have him back nonetheless."