The £1million striker fractured his left leg during training on Thursday and faces a lengthy spell on the sidelines.
Rangers are also sweating on the fitness of midfielder Akos Buzsaky, who aggravated an ankle injury on international duty with Hungary last week and was forced to miss Saturday's goalless draw at Ipswich.
Skipper Martin Rowlands is in contention for a start after coming off the bench at Portman Road following a neck injury.
Left-back Damien Delaney serves the second game of his two-match suspension so Damion Stewart could keep his place in the back four.
Back-up goalkeeper Jake Cole is still recovering from a minor elbow operation.
Preston boss Alan Irvine hopes to have Callum Davidson and Simon Whaley available for the trip.
The pair suffered knocks which forced them off during last weekend's victory over Sheffield United, which took North End to the brink of safety.
Defender Davidson was forced from the action as a precautionary measure at half-time when a locked pelvis threatened to cause further muscle damage if he continued.
Winger Whaley took a blow to the body late on during the 3-1 success and was similarly withdrawn.
However, Irvine is hopeful both players will be fit for the Loftus Road clash and the Deepdale boss is again expected to pair Neil Mellor and Chris Brown in attack.
Watford striker Tamas Priskin's loan spell ends after the game while defender Liam Chilvers (Achilles) and midfielder Kevin Nicholls (knee) remain sidelined.