The 25 year old, City's top scorer, has returned to training after missing four games with a hamstring injury, but is not yet ready to play in Saturday's clash with Southampton at the Etihad.
"Sergio is okay. He has worked just now with the squad but he just started on Thursday, so he needs more work to be 100 per cent fit," said Pellegrini.
"He is not in the squad but he doesn't have any problems with his injury.
"For this week it is too soon for him to start playing because he just worked two days, but next week against Liverpool he will not have any problems."
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