Full-back Justin Hoyte and striker Scott McDonald became the latest men to join the ranks of the walking wounded after last Friday night's 1-0 npower Championship defeat at Leicester.
Hoyte has a hip problem, while McDonald complained of a tight hamstring, and both will undergo tests before decisions are taken.
Central defender Jonathan Woodgate, who damaged a calf muscle in the 3-1 defeat at Derby on New Year's Day, is working his way back to full fitness, as is striker Ishmael Miller, who picked up an ankle ligament problem against Watford on January 12.
Utility man Andy Halliday underwent surgery on his broken nose on January 7 and like Woodgate and Miller, is being assessed, while midfielder Muzzy Carayol could return to the squad following knee surgery.
Striker Curtis Main (knee) is stepping up his comeback and Julio Arca (toe surgery) is expected to return to training in two to three weeks.