The Brazil international goalkeeper will miss 6-to-8 weeks after picking up an injury in training, with QPR boss Harry Redknapp bemused to see him still at the club.
Cesar, who was heavily linked with a move away from Loftus Road during the summer transfer window following the Rs' relegation from the Premier League, suffered the injury in training on Tuesday and is expected to be sidelined until the end of October.
The former Inter and Flamengo star has not featured for QPR this season, with manager Harry Redknapp admitting prior to Wednesday's goalless draw with Brighton that the veteran is not in his plans and facing a tricky dilemma, as Cesar has one eye on next year's World Cup in his home country.
"It's a difficult situation with Julio, and I'm surprised no one came in for him," Redknapp told reporters. "I don't know whether Julio wants to sit on the bench. His dream is to play in the World Cup in Brazil, and I don't think this will affect his situation.
"The manager of Brazil thinks he's the No. 1 man, and I don't think anything that happens at QPR is going to change that for him."
QPR has also been dealt another injury blow after it was confirmed that striker Bobby Zamora has undergone surgery on a knee problem that will rule him out until the end of December.