Clinical finishes from Wayne Rooney, Daley Blind and Juan Mata and some electrifying wing play from Anthony Martial lifted the gloom, however, and a well-deserved 3-1 win kept alive United's hopes of a first Cup triumph since 2004.
"I will go back home and wine will be ready. An expensive wine. It is from Ed Woodward," former Barcelona and Bayern Munich coach Van Gaal, who on Thursday accused the media of "sacking" him three times already this season, told reporters.
"I liked the performance in the first half, it had a lot of confidence and that is back which is very important.
"The second half was even better, we created a lot of chances and we scored goals. But also we created more chances to score more goals. I am a very happy coach."
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Van Gaal's side have managed only 12 Premier League goals at home this season and fans have become increasingly disgruntled by the style of football being produced.
A turgid 1-0 home defeat by Southampton last weekend left United 10 points adrift of leaders Leicester City and five behind fourth-placed Tottenham Hotspur, who occupy the last spot that qualifies for the Champions League.
With former Chelsea boss Jose Mourinho favourite to replace Van Gaal, should the axe fall, the pressure has begun to tell on the 64-year-old who said before kickoff on Friday that it had been hard to enjoy his job in recent weeks.
What was clear on Friday, though, was that the players were still giving 100 percent for the cause.
Left-winger Martial was a threat all night, creating numerous chances, while Rooney's opening goal was a cracker.
"I think in the first 20 minutes (Martial) was very bad. But after that he was fantastic," Van Gaal said.
"I am very happy that he is a Manchester United player because I think he shall be a great player for Manchester United for a long time."
Van Gaal also praised the 5,000 United fans who cheered the team on, albeit with his tongue firmly in his cheek.
"It is unbelievable and still they come to look at 'boring' Manchester United. It is fantastic – amazing!" he said.
(Reporting by Martyn Herman; editing by Ken Ferris)
