Sir Alex Ferguson has revealed Nemanja Vidic is likely to miss Saturday's Premier League title showdown with Chelsea at Stamford Bridge after he missed the Barcelona game with a stomach problem.
But Ferguson believes the Premier League leaders coped well against the Catalans without the Serbia defender.
'Without Vidic, it meant the reshuffle,' he explained.
'I decided to go with Wes Brown because of experience. It would have been a bit unfair to place the responsibility on Gerard Pique against his old club. (Rio) Ferdinand played well and looked strong throughout the game.'
The defender received hospital treatment for a stomach problem on last night and was forced out of tonight's game.
Ferguson confirmed Vidic had a stomach infection and is unlikely to return against Chelsea.
'He was 24, 36 hours without eating,' the United boss explained.
'He had some soup this afternoon, but wasn't ready to play. I don't think he'll be ready for Saturday, that's the situation, it's a stomach infection, (although) we don't know what kind of infection it is.
He added: 'Yesterday before training, he had very severe stomach pains, so we sent him off to a hospital only about a mile away.
'We felt that was the best place for him to go. He was kept in until late at night and then they let him go.'
Ferguson also claimed Manchester United would have beaten Barcelona in tonight's Champions League semi-final first leg had Cristiano Ronaldo been given more support by his team-mates.
He said: 'In Cristiano Ronaldo, I thought we had a player who could win the match. He was a constant threat and I thought that, with better support, we could have won.'
Ferguson felt let down by his side's midfield, saying: 'I am bit disappointed in the transition between defence and attack.
'We are normally better at keeping possession of the ball, that causes more concern than any other part of the game.
The United boss also claimed his side surrendered possession too often.
He said: 'We will analyse (why we didn't score) in the next two to three days, but we lacked penetration. We were not quick enough out of central areas and when you give the ball away at this level, you have to go back and defend.'
Wayne Rooney and Park Ji-Sung were asked to play in unfamiliar roles and Ferguson believes those changes affected his side.
'Asking Rooney to play a different position and Park as well obliged us to defend more,' he said.
The veteran manager claimed Paul Scholes - making his 100th Champions League appearance - was United's best player
'Scholes was probably the best player, with confidence and belief in his own ability always there,' he said.
Despite his side's subdued performance, Ferguson was satisfied with the result.
'When you get the result, you have to look at the plus points and there were some plus points; 0-0 in the Nou Camp is not a bad result,' he said.