"Yaya has a muscle injury. We will see with the doctor how many days," Pellegrini told a press conference.

"Maybe it is not so hard as we thought at the beginning, but I think he needs at least 10 days or two weeks to recover."

One of City's outstanding performers this season, Toure appeared to sustain the injury as he shot at goal in the early stages of his side's 3-2 loss at Liverpool in the Premier League on Sunday.

News of his unavailability arrives at an untimely moment for Pellegrini, whose side are currently seven points behind league leaders Liverpool with two games in hand.

Toure, 30, stands to miss the forthcoming home matches against Sunderland and West Bromwich Albion, as well as the trip to Crystal Palace on April 27.

Pellegrini was able to provide more optimistic news on captain Vincent Kompany and top scorer Sergio Aguero.

Belgium centre-back Kompany suffered an injury scare in training prior to the game at Liverpool and was culpable for the home side's winning goal after slicing a clearance straight into the path of Philippe Coutinho.

However, Pellegrini said that he would be fit for Wednesday's game against Sunderland, along with Aguero, who made his return as a second-half substitute at Anfield after five games out with a hamstring problem.

"Vincent is fine. He is on the squad list for tomorrow (Wednesday) and so is Sergio Aguero," Pellegrini said.

"We'll see tomorrow who starts. It's important we start with the same high performance we showed in the second half of the Liverpool game."

Despite Liverpool's current advantage, Pellegrini believes that his side can still win the title if they win their two games in hand.

"We win our two postponed games and we're a point back," he said. "If you don't believe we can do it, you can't believe in anything."