On-loan Reading man Davies scored two exceptional goals during last weekend's defeat at the hands of Walsall - including a 40-yard free-kick - but the Royals have yet to decide whether to allow him to feature in the competition.
Davies has extended his loan spell at Adams Park until January 4 but either Matty Bloomfield, Stuart Green or John Mousinho will replace him if Reading veto his appearance.
Forward Stuart Beavon remains sidelined after having groin surgery but manager Gary Waddock has no other selection dilemmas as he looks for a first win since taking charge last month.
