Brentford boss Thomas Frank is wary facing Manchester United on Wednesday night.
Frank says the trip will be the hardest of the season.
He said: We are potentially going into the most difficult game of the season, with everything taken into consideration.
We are going away to the biggest away ground, with those fans, against a very good side that are much more stable.
Erik ten Hag and his staff have done a very good job. They've just won their first trophy and they're fighting for a Champions League spot.
They lost (on Sunday) so they will want to bounce back. Plus, we beat them last time, so they'll doubly want to bounce back. And they're a very good team with top players."