Manchester City midfielder Samir Nasri will be sidelined for the rest of the season with a groin injury.
The France international was forced off during City's 1-0 Premier League win at Tottenham last weekend, leaving the field shortly after being introduced as a 73rd-minute substitute.
"We have the complete squad working except for Nasri, who has a muscle injury," said Pellegrini. "He will be out from now to the end of the season."
Pellegrini could, though, welcome back captain Vincent Kompany, who has been absent since last month's Manchester derby with a thigh issue.
"Vincent is always an important player for us," added Pellegrini. "He is coming back from a muscle injury.
"It is important for him to recover his normal performance. We will see what will happen from now until the end of the season."
City host QPR on Sunday as they continue their bid to claim second behind champions Chelsea.
‘It was without a doubt one of the most important matches that I played in my career. It wasn’t just Champions League football – it was a whole club at stake’: Ex-Chelsea star opens up on key game which changed the Blues' fortunes forever
'I was Arsenal captain and really enjoyed it, but when Man City come calling, you have to listen': England international reveals reason for swapping London with Manchester
