Rooney was dismissed by referee Kim Milton Nielsen in the 63rd minute for ironically applauding the official after being shown a yellow card. United came closest to scoring when Gonzalo Rodrigo cleared off the line from Ruud van Nistelrooy.
But Edwin van der Sar also saved brilliantly from Rodolfo Arruabarrena. Rooney's red card, however, will overshadow a relatively satisfying result for United. But it will also again raise serious questions about his temperament after a hot-headed display in England's World Cup qualifying defeat against Northern Ireland.
United were without captain Roy Keane, out for three weeks with a hamstring injury, but Cristiano Ronaldo declared himself ready to play following the death of his father. And Sir Alex Ferguson's side almost struck a crucial early blow when Mikael Silvestre's 17th-minute header was well saved low down by Sebastian Viera.
But they suffered a blow when defender Gabriel Heinze suffered a knee injury in an innocuous challenge. He struggled on after lengthy treatment, but was eventually replaced by Kieran Richardson.
Goalkeeper Van der Sar then emphasised his growing importance to United with a brilliant stop from Arruabarrena after 37 minutes, diving to his left to save as a goal looked certain. But it took a goal-line clearance of breathtaking quality from Rodrigo to deny United four minutes before the interval.
Van Nistelrooy pounced after Viera dropped Ronaldo's free-kick, but Rodrigo somehow overhead-kicked his effort off the line. Little had been seen of former United striker Diego Forlan, but he had his first opportunity after 50 minutes, only to curl the ball wide from a good position.
Rooney was then idiotically sent off - and there can be no excuse for the behaviour that led to his red card. He had been booked by Danish referee Nielsen, famous for sending off David Beckham in England's 1998 World Cup clash against Argentina, for a foul on Quique. But he then responded by sarcastically clapping the referee inches from his face, leaving Nielsen with no option other than to send the England youngster off.
It also left United hanging on, and Juan Pablo Sorin should have done better than to shoot straight at Van der Sar after he was set up by Marcos Senna. And United almost paid the ultimate price for Rooney's stupidity in the last minute when Senna's free-kick skimmed the bar off Rio Ferdinand's deflection., BBC News reports.