Midfielder and stand-in skipper Mahon has missed the last two games after picking up a hip injury in training, and centre-half Stewart sat out the midweek draw against Crystal Palace with an ankle problem.
Mahon should reclaim his place in midfield at Hillsborough with Rangers having picked up just one point in his absence, but Stewart may have to settle for a place on the bench with Fitz Hall (groin) returning against Palace.
Rangers are still without defender Matt Connolly, although he has resumed full training after finally recovering from glandular fever and could be back in a fortnight.
Lee Cook, Alessandro Pellicori (both knee), Angelo Balanta (hernia) and captain Martin Rowlands (cruciate) remain sidelined.
