United will more than likely finish the season trophy-less after former striker Danny Welbeck knocked them out of the Cup with a late winner.
Van Gaal’s side will now focus on finishing in the top four of the Premier League and qualifying for next season’s Champions League.
Keane believes the Dutchman will come in for criticism following the result last night but insists he needs to be given time to rebuild a club as big as United.
“It takes time, he’s only been in the door five minutes.
“A lot of fans don’t understand the game and how much of a challenge it is to run a club the size of Man United. They should’ve given David Moyes more time, but they didn’t.”
With Arsenal, Liverpool and Tottenham Hotspur all gradually improving, things aren’t looking good for United at the moment with their upcoming games.
The team head into a tough run of fixtures in March and April and their place in the top four is far from certain, so United will need to dust themselves off and quickly in order to prepare for a clash against Spurs on Sunday.