City lie in third spot in the Premier League table, but their struggles in the Champions League and Capital One Cup and no victory in three games has done little to brighten the mood at the club.
Pellegrini also suffered a blow in midweek when David Silva suffered a knee injury in the 2-0 defeat to Newcastle United, leaving the Spaniard to spend the next "three to four weeks" on the sidelines.
United make the short trip across the city buoyed by their last-minute draw against league leaders Chelsea last weekend.
Louis van Gaal's team weren't overly convincing at times, but it was an improvement from some of their previous performances and they only sit one point behind Arsenal and Liverpool in the standings.
Captain Wayne Rooney returns after sitting out the last three games through suspension, with the England international also overcoming an ankle knock to start on Sunday.
Midfielder Ander Herrera could be included by Van Gaal after only featuring on the bench against Chelsea.
Manchester City: DWWDLL
Manchester United: WLWLDD
Possible starting lineups
Manchester City: Hart; Zabaleta, Kompany, Mangala, Clichy; Toure, Fernando, Navas, Milner; Aguero, Dzeko
Manchester United: De Gea; Rafael, Smalling, Rojo, Shaw; Blind, Fellaini; Herrera, Di Maria; Rooney; Van Persie
Sports Mole says: 2-1