The Ivory Coast international has failed to live up to the high standards he has set at the Premier League club in the first two months of the campaign.
Toure has scored just twice this season and the marauding midfielder, who came on as a substitute late in Saturday's 4-1 hammering of Tottenham, has not looked fully fit
The former Barcelona man will be expected to return to the starting line-up for City's crunch clash with CSKA Moscow in the UEFA Champions League on Tuesday and Pellegrini believes the 31-year-old is improving with every game.
"Yaya has the quality to make a difference. He had a difficult summer but every game he is getting better," the Chilean said.
Tuesday's game will be played behind closed doors as punishment for racist abuse and crowd trouble involving CSKA fans.
Pellegrini will miss the presence of City fans at Arena Khimki, but urged his side to get the job done in their absence.
"It is going to be strange [playing without fans] but we have to focus on being ourselves," he said.
"It is a pity we cant play for fans, as this competition is for the fans. But we don't have any other option."
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