Blackburn score a fine opener
Marvin Emnes played in Graham, who fired into the corner past Sergio Romero with a strike that was so good, it had Jose Mourinho applauding on the sidelines.
Manchester United equalised on 27 minutes, with Marcus Rashford rounding the goalkeeper after a brilliant through ball from Henrikh Mkhitaryan.
United throw on Pogba and Zlatan
Just after the hour, with the score at 1-1 and Manchester United expecting a busy week of cup football, Jose Mourinho brought on some serious super subs.
Paul Pogba and Zlatan Ibrahimovic combined for the goal that put Manchester United 2-1 up on 75 minutes.
The win was rewarded for Manchester United with a quarter-final tie against Chelsea, at Stamford Bridge.