Arsenal boss Arsene Wenger is confident of a big performance from William Gallas against former club Chelsea tomorrow.

Gallas was fined and stripped of the Arsenal captaincy for criticising team-mates last week, but Wenger, the manager, believes that the 31-year-old's mental state is not a cause for concern as he returns to Stamford Bridge to endure what is likely to be a virulent reception.

"Focus on what you do," Wenger advised. "Personally, I don't think it's very difficult and I've got a lot of stick in my career. He's a strong character and it's a good job - he will need to show that on Sunday."

Wenger acknowledged that he was worried about how Gallas would react to his demotion, but said that his behaviour in training and in the Champions League win over Dynamo Kiev on Tuesday had helped to repair his standing among his team-mates.

"Anything can happen when you make this kind of decision," Wenger said. "You can be off or you can say, 'I want to win'. Your attitude can always gain you credit or lose you credit and I think in the kind of attitude he has shown, he has gained credit."