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The Ivory Coast international has struggled for form and fitness since returning from the World Cup this summer, with his display in the 1-0 Champions league defeat to Bayern Munich coming in for particular criticism.
However, Pellegrini insists he has no concerns over his star midfielder and believes he is 100% committed to the club, despite the summer speculation surrounding his future.
‘It is not fair for me to criticise what Yaya did in the last game,’ he told Sky Sports reporters.
‘In this team - at least in my way of thinking - when we win or lose it is because all the team did well or did bad.
‘I think everyone knows what his best performance [is], of all the players, and are trying to reach that performance, all of them.
‘I don't agree Yaya has all the responsibility about the game we played. Yaya always has commitment with the team and the squad, and his mates. He doesn't have problems about that.’
Pellegrini also confirmed at his press conference that injured pair Sefan Jovetic and Fernando would not be returning in time for the weekend, but striker Sergio Aguero would be in line to start, having been left on the bench for the UCL loss.
‘Sergio in this moment is not ready to play three games in a row in one week,’ he was quoted in the Manchester Evening News.
‘That's why I thought it was better for him and for the squad not to play him for 90 minutes against Bayern.
‘He's fresh for Sunday and I am sure that we will make a difference.
‘When he is 100% fit he makes a difference.’
The major selection talking point, however, has been whether loanee Frank Lampard will feature against his former club, following speculation upon his arrival this summer that the Stamford Bridge legend remains reluctant to face his old teammates.
That is not the case, though, according to Pellegrini, who is more than prepared to give the ex-England international a run out.
‘Frank is part of our squad and tomorrow I will give the squad list for that game. For sure he will be involved in that game. He is part of the squad,’ he said.
‘I don't think it is a difficult situation for him. I think Frank didn't continue at Chelsea because they didn't want him, not because he wanted to come here to Manchester City.
‘He can't continue playing in the team he played his whole life, but he has all the rights to continue playing football. He arrived here and we are very happy with him.’