The reigning Premier League champions take on the league leaders at Stamford Bridge on Saturday, but Jose Mourinho will be unable to call upon his top scorer after Costa was handed a suspension for stamping on Liverpool’s Emre Can in the League Cup semi-final second leg.
Chelsea unsuccessfully challenged the charge, meaning the former Atletico Madrid frontman will miss games against City, Aston Villa and Everton.
While Pellegrini admits the Blues will be worse off without Costa, who has scored 17 league goals this season, the Chilean is convinced that the ban could be a good thing for the Spaniard and may help reform some of his more volatile ways.
“I think he is a very good player, a very important player,” said the City boss ahead of his side’s meeting with Chelsea.
“Maybe he is not an easy character, but I hope with this punishment that it will be a good thing for him for him to change a little bit in the future.
“He does not need to do that kind of thing because he is a top player.”
Pellegrini, meanwhile, also confirmed that Sami Nasri could make a return to the squad for the trip to west London, also playing down the significance of the game in the race for the title.
