Rock-bottom Rangers are seven points adrift of safety in the Barclays Premier League heading into the match with Sir Alex Ferguson's league leaders.
With 12 matches remaining, victory would be huge for QPR but an already unenviable task has been made more difficult by a lack of attacking options.
Deadline-day moves for Peter Crouch and Peter Odemwingie fell short, meaning Zamora and Remy are the men charged with shooting QPR to survival.
However, both are struggling with injury and Redknapp today revealed the latter almost certainly faces surgery on a long-standing hip complaint.
Zamora has made four substitute appearances since returning from a two-and-a-half-month spell on the sidelines and has not played more than 45 minutes in a match since the 1-0 defeat to Arsenal on October 27.
"Maybe Bobby will need an operation at the end of the season," Redknapp said. "I am not sure, he probably will do.
"The aim is to keep him going for the last 12 games of the season if we can because he is that important to us. We'll see how we go tomorrow with him. The longer we can get out of Bobby, the better.
"We're hoping we can get more than just half a game from him. It is up to the fitness people and the physios to try and push him on to longer if we can."