UEFA CHAMPIONS LEAGUE:WHEN A footballer as important as Nemanja Vidic goes down with a stomach bug the night before a Champions League semi-final, a manager could be forgiven for thinking that his luck is out.

Alex Ferguson will certainly have been cursing Vidic's rotten misfortune, as well as his own, as he was forced to reconfigure his defence to face one of the world's most devastating forward lines.

In the end the Manchester United manager is entitled to take great satisfaction from the way United's defence, minus Vidic - who was too ill to go to the stadium and watched the game from the hotel - kept Barcelona at bay to keep a clean sheet in difficult circumstances.

Granted there were some hairy moments for Wes Brown and there was even the rare sight of a flustered Rio Ferdinand kicking the ball out for a corner when hardly under any pressure. United never looked as comfortable when Brown, rather than Vidic, is partnering Ferdinand yet, overall, the defence coped admirably with the last-minute changes that was forced upon Ferguson.

Vidic had missed training on the evening before the match for two reasons. First, he needed treatment for the knee injury he suffered in the quarter-final against AS Roma. More seriously he had also complained of feeling ill on the flight from Manchester. He was able to take his seat next to Ferguson for a press conference at the team hotel and could be seen laughing and smiling when he was asked how he planned to stop Lionel Messi.

But when he returned to his room his condition quickly deteriorated. The club's doctors diagnosed him as having a fever and gastroenteritis and, as his condition worsened, they were sufficiently concerned to knock on Ferguson's door and tell him the situation was serious.

Vidic was taken to Barcelona's Hospital de Bellvitge where he was seen for two hours before being placed on medication and returning to the hotel.

The timing could hardly been worse from United's perspective, Vidic's robust presence being a significant reason why Ferguson's men have the most impressive defensive statistics in English football. It led to an emergency meeting between United's management and coaching staff and Ferguson was so anxious for the news not to get back to Barcelona that he ordered the illness to be kept secret.

Yet the presence of a 6ft 2ins, broken-nosed Serbian international defender in a hospital waiting-room the evening before a Champions League semi-final was never going to go unnoticed.

The news slowly seeped out and, late on Tuesday, Frank Rijkaard took a call at home telling him that he could start planning for a United side that would be missing one of its more indomitable characters.

Vidic's condition was described as "not serious" but, for United, there were potentially grave repercussions. Mikael Silvestre had deputised in training but the Frenchman had started only one game since returning from a serious knee injury.

Gerard Pique, meanwhile, was considered too inexperienced at such a refined level. So Ferguson took the best decision available to him by moving Wes Brown into the centre of defence and replacing him at right-back with Owen Hargreaves.

The task for Hargreaves was to subdue Andres Iniesta whereas Brown had to show Vidic was not irreplaceable. Yet even a player of Vidic's stature would have struggled at times with the exhilarating speed, touch and vision of Barcelona's pass-and-move football.

Messi seemed intent on bewitching this majestic old arena, subjecting Patrice Evra to the kind of examination he rarely experiences in the Premier League. Hargreaves will be grateful Messi was on the other side of the pitch as Barcelona took command of the first half and United's defence was put under pressure because of the team's inability to keep the ball in midfield. United's failures at this point were encapsulated by Edwin van der Sar who misdirected a goal-kick straight to an opponent.

The best news for Ferguson is that when Barcelona travel to Old Trafford next week they will be facing a side that should have its strongest defence available. It is difficult to imagine Vidic losing possession as cheaply as Brown did early in the second half, a mistake that almost led to Samuel Eto'o scoring. In the end, however, every member of this new defensive quartet can be satisfied with their evening's work. Guardian Service