The midfielder is forced to sit out one game after picking up a fifth yellow card of the campaign during the 1-0 defeat against rivals Wolves last weekend.
Midfielder Papa Bouba Diop is among those pushing to replace Mullins after impressing for the club's Under-21 side in recent weeks.
Defender Jonathan Spector is out with an ankle injury, while midfielder Darren Ambrose misses the chance to face his former club as he is still sidelined with a knee injury.
But boss Lee Clark is expected to have Pablo Ibanez and Nikola Zigic available, after the pair returned to training following injury.
Full-backs David Murphy and Stephen Carr (both knee) are long-term absentees while striker Akwasi Asante (hamstring) remains sidelined.