Manchester City were honourable at Etihad as they overturned an early 0-1 lead of West Brom to 2-1, keeping them at fourth position on the premier league table.
Stephane Sessegnon beat Joe Hart in six minutes of play, putting the visitors on the drivers seat and keeping them under pressure.
Sergio Aguero converted a penalty kick into a goal after Aleksandar Kolarov was brought down in the penalty box, making Pellegrini men finish the half time to draw.
Nasri who returned from injury tapped the ball into an empty net with 25 minutes remaining to put City four points above rivals Manchester United.
Manchester City are now relaxed as they prepare to host PSG who will come visiting on Tuesday in the champions league.