Wayne Rooney is a major injury doubt for England's friendly with Egypt at Wembley on Wednesday.
Rooney came off the bench to score his 28th goal of the season and win the Carling Cup for Manchester United against Aston Villa on Sunday.
But Sir Alex Ferguson confirmed the 24-year-old was feeling slight discomfort in his knee afterwards.
Rooney will be allowed to join up with the England squad this evening but will be assessed by team medical staff before Fabio Capello knows whether he has his talisman available to face the African Nations Cup winners.
"He got a whack right away," said Ferguson.
"He has been complaining a little about that for a few weeks and was holding it a bit today. In fact I thought we might have to take him off but he wanted to stay on so it was good.
"The doctors are assessing it and I don't know what England are going to do."
Ferguson revealed he knew weeks ago that Rooney would not be starting the Wembley showpiece, having decided to pair Dimitar Berbatov and Michael Owen in attack.
Owen grabbed United's equaliser with a typical poacher's effort before picking up a hamstring injury the former Real Madrid man feels will keep him out for a number of weeks.
Rooney needed no prompting to get involved and marked the occasion by looping the late header past Brad Friedel to give United the trophy for the second year running.
"I was chomping at the bit to get on," he said.
"You want to play in finals. Thankfully I have managed to do so and left my mark on the game.
"I knew on Wednesday or Thursday I wouldn't be playing. I had a little bit of a stomach bug and the manager was looking for an excuse to leave me out.
"When he found out about that it made his mind up.
"I was still disappointed but it was the correct decision by the manager."
Worries about Rooney's availability for the Egypt game will only heighten fears that too much is being asked of a man who is so important to both club and country.
But he is not concerned about burn-out, and neither is he setting himself any scoring targets, even though he is only two short of the 30 mark Ferguson has put down as a very conservative aim.
"I don't feel any pressure or burden really," he said.
"To be honest I have probably had pressure since I was 16 so it is something you get used to and deal with in your own way.
"I have done that and it is not something I am going to get concerned about now.
"I am enjoying playing at the minute and enjoying scoring goals. Hopefully that will continue.
"Cristiano got 42 but I am just looking to contribute to us winning medals."