Toure played a starring role as City beat Dynamo Kiev in the Champions League and Liverpool in the League Cup last week but was missing on Wednesday as Jurgen Klopp's side got their revenge in the Premier League.
The Ivory Coast international divides opinion among City fans, with some insisting that he is either lazy or past it - or both - while others reflect on the important role that he has played in the club's recent history.
But Pellegrini is firmly behind his midfield stalwart. "When Yaya plays, you always ask me why I don't take him out and, when Yaya doesn't play, you miss Yaya!" he replied when asked about Toure's influence. "He will always be a very important player here, in every club that he plays."
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Toure is expected to leave the Etihad Stadium this summer after his outspoken agent, Dimitry Seluk, claimed that the arrival of Pep Guardiola as manager would herald the end of his City career.
Pellegrini, whose own summer exit is confirmed, says that neither he nor Toure are thinking about what will happen next season but insists that the midfielder will be an influential figure whether he stays or goes.
"I don't know because I am not thinking about that and neither is Yaya, what happens next year in this club," he remarked, "but, in every team he plays, he will be an important player - not only in the dressing-room but on the pitch.
"I think, [over] 90 minutes, he brings quality and all the players trust in him because he makes an important difference. In the dressing-room he is one of the few players, with Martin Demichelis, that has played a final of the Champions League so I think all of them are talking about that also so he is important in the pitch and in the dressing-room."