Ok maybe they were tired but there was only 10 mins left, surely the adrenaline of being 2-1 up against Man Utd would take them through! Have you ever played football?!
Not just the fact he took them off its the choices of subs and the positions.
When your a smaller team against one of the best, winning in the last few mins it's going to be backs against the wall. What you dont need is a guy who's too short to hold the ball up on his own up front and a guy who doesn't close down, chase the ball, tackle or put in any noticable effort!