Defender Ayala, on loan from Norwich, missed the 2-1 home defeat to Hull last weekend due to illness.
Sean O'Driscoll's side came through that game without any new injury problems.
Defender Greg Halford (calf), midfielders Radoslaw Majewski (ankle) and Jermaine Jenas (calf) and striker Simon Cox (foot) were all absent against the Tigers and will remain on the sidelines for Saturday's match.
As well as Ayala, Reds boss O'Driscoll has defender Brendan Moloney, midfielders Guy Moussi, Henri Lansbury and Lewis McGugan and strikers Robbie Findley and Dexter Blackstock available should he wish to make any changes to his starting line up.
- Sports & Recreation
- Greg Halford
- Jermaine Jenas
- Radoslaw Majewski