Roy Hodgson admitted Fulham's 1-0 defeat by Hull was the worst possible preparation for Saturday's FA Cup tie against Manchester United.
Manucho tucked home Richard Garcia's cross two minutes into injury time to give Hull's Barclays Premier League survival bid a crucial shot in the arm.
"Of course the team will now need lifting for United," said the former Inter Milan coach. "There's no worse way to lose a game than to play well, stare at a 0-0 draw when you think we should have scored and then to lose in the 92nd minute."
He added: "You couldn't write a worse scenario for a player or coach than that. This is the ultimate football nightmare that you have to live through."
Hodgson will investigate claims made by Fulham defender John Pantsil that he was abused towards the end of the match.
Pantsil was clearly angry as he left the pitch, though it was unknown whether the abuse came from fans or opposition players.
"The referee said to me that John complained to him about being abused by somebody," said Hodgson
"The referee didn't hear anything so he couldn't take any action. I'll investigate it with John.
"If John feels we as a football club need to do something about then we'll explore it."
Copyright (c) PA Sport 2009, All Rights Reserved.