O’Neil was stretchered off in the 3-0 midweek defeat to Blackpool at home after taking a bang to the head.
However, the problem was not as bad as first feared and despite the midfielder having a niggling calf injury, he should be fit.
Marcus Bent should also return to the squad after overcoming a slight hamstring problem, but fellow forward Jeremie Aliadiere is still ruled out after an ankle operation.
Jonathan Franks (thigh) returned to training this week, Didier Digard is out for two to three weeks after twisting his back, while Sean St Ledger plays the last game of his loan deal.
The defender will be available again in the New Year when he pens a permanent deal.
The match kicks off at 1.15pm.