Manchester United boss Louis van Gaal admits Marouane Fellaini was key to their victory over FA Cup opponents Cambridge United.

After failing to break down Cambridge in the first tie at the Abbey Stadium, the policy of having another route to goal paid off against the League Two side at Old Trafford.

"With Fellaini, we have always also an attacking point through the air," van Gaal told MUTV. "Cambridge have very tall players and we could score also in the air and not only along the floor. That was our game plan and he [Fellaini] confirmed that [his aerial prowess] again.

"I think we could have scored more goals. In the second half, we played a little bit more forward and I believe we created more chances. Robin van Persie had four possibilities so we could have scored more but I am very happy the first chance of the match, for Cambridge, was against the post."