Manchester United manager Alex Ferguson criticised Wayne Rooney for his sending off in his side's 0-0 draw at Villarreal just when they were beginning to get the upper hand in their opening Group D match.
The England striker was dismissed with 26 minutes to go when he received two quick-fire bookings from Danish referee Kim Milton Nielsen, first for a foul on Villarreal defender Quique Alvarez and then for sarcastically applauding the decision.
"I think that Wayne reacts to injustice a bit," Ferguson told a post-match news conference.
"He felt that it was a wrongful booking but you can't applaud a referee. At first I thought he put his hand on his arm, but he had clapped the referee. So he's given himself no chance whatever, not with that referee.
"He's a young lad of 19 years of age and we hope that with maturity these things will evaporate. We hope to retain his strengths and good points and eradicate the bad ones."
Ferguson admitted that the Rooney sending off stopped United in their tracks just when they were beginning to dominate the game against Champions League debutants Villarreal, but he praised his defence for keeping the Spanish side at bay for the rest of the match.
"We were getting control at that point and having our best moments, but with 25 minutes to go and down to 10 men I think we did the job and the back four improved magnificently in the second half and did really well.
"Home strength is a key factor for us and on the evidence of tonight we just about deserved a point. It was an efficient performance as well as a reasonable result."
Rooney will now miss United's second match at home to Benfica and Ferguson revealed that the Premier League side had suffered a further setback as Argentine fullback Gabriel Heinze had suspected ligament damage to his knee.
Villarreal coach Manuel Pellegrini said that beginning the group stage with a point was positive, but he was disappointed not to have gained a victory at home.
"I wouldn't say I was satisfied, but I am calm because it was very difficult to break down the Manchester United defence," he said. "The team played well, but it isn't good to let slip points at home."