Premier League leaders Chelsea host the defending champions Manchester City on Saturday evening at Stamford Bridge and Jamie Redknapp says Pellegrini's side must respond after recent 2-0 defeats to Arsenal and Middlesbrough [in the FA Cup].
With the Blues top striker Diego Costa and Man City's Yaya Toure missing out on the heavy weight clash tomorrow, there'll still be a lot to talk about in the match.
Mourinho's side are five points clear off second-place City at the top of the Premier League table and a win for the west London club will be a big disappointment for Pellegrini who is looking to cut the deficit in the table by preventing a third defeat in row in all competitions.
"Chelsea are in pole position, knowing a win will put them eight points clear, while Manchester City, after two bad results, have really got to show us what they’re made of and demonstrate the character that won them the title last year and in 2011/12," Redknapp told Sky Sports.
"Defeat could leave City in a position where Chelsea’s lead is just too much and, if the home side do win on Saturday night, I’m sure lots of people will be saying the title race is over.
"Chelsea have got the bit between their teeth - Jose Mourinho has got the whole club believing the world is against them and that they’re the underdogs when they really aren’t – and if they were to not win the title after being eight points clear that would be an incredible turnaround," the former Liverpool and Tottenham midfielder continued.
"However, if Chelsea do win, I don’t think we should write-off City just yet, given the quality they possess. They battled back from eight points behind Manchester United to win the Premier League in 2011/12 and were trailing Liverpool by six last season.
"Manuel Pellegrini will be desperate to see a response from his side in this huge match, though, after losing to Arsenal and going out of the FA Cup to Middlesbrough last time out.
"Unfortunately for him, they’ll have to do it without Yaya Toure, who is still away at the Africa Cup of Nations.
"City’s record without the Ivory Coast midfielder in their side speaks for itself: they haven’t won a league game without him this season.
"Toure is a huge loss for a match like this. People were very quick to criticise him earlier in the season but he can dictate games and takes an awful lot of pressure off David Silva. Without him they’re not half the team they are when he’s playing.”