The Ivory Coast international was instrumental in City's 2013-14 title-winning campaign, scoring 20 Premier League goals in 35 appearances as Pellegrini's men clinched the crown by two points ahead of Liverpool.
After representing his country at the World Cup in Brazil, Toure has featured in three of City's four top-flight matches so far this term.
The 31-year-old missed last weekend's 2-2 draw at Arsenal, and was far from his best in City's last-gasp 1-0 defeat at Bayern Munich in the UEFA Champions League on Wednesday.
Toure's lethargic performance at the Allianz Arena has drawn widespread criticism in the media but, speaking on Friday, Pellegrini jumped to the defence of the former Barcelona man.
"I don’t agree that Yaya has all the responsibility for the games," he said. "He always has commitment."
Pellegrini also commented on the fitness of Sergio Aguero, who came off the bench for a late cameo in Munich.
"When he is 100 per cent fit, Sergio always makes a difference," he said.
"At this moment he is not ready to play three games in one week."
New signing Eliaquim Mangala is yet to feature for City, with captain Vincent Kompany forging a strong defensive partnership with Martin Demichelis.
But Pellegrini insists the France international is simply adjusting to his new surroundings.
"He has no problem and he is working with the squad," he said. "He started late in his preparation."
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