Bristol City will be without Liam Fontaine and Marvin Elliott.
Captain Fontaine has been sidelined by a knee injury since the goalless draw with Nottingham Forest on December 17 and is expected to remain out of action until the beginning of February.
Veteran defender Louis Carey is likely to continue to deputise in Fontaine's absence. Carey played at the heart of defence in both 1-0 victories over Southampton and Millwall over the course of the New Year period.
Midfielder Elliott tweaked his hamstring in the very early stages of the success against Millwall on Tuesday night and will not recover in time to face the Red Devils.
His injury is not expected to take too long to heal, but in the meantime Kalifa Cisse is set to fill the role in central midfield.
Crawley will check on Matt Tubbs and Dannie Bulman.
Striker Tubbs, who has scored 16 goals this season including a hat-trick against Redbridge in the second round, missed Monday's 1-1 draw with Oxford due to a groin injury.
His place was taken by John Akinde, who joined Crawley from Ashton Gate in the summer and will be hoping to face his former club.
Midfielder Bulman also missed out against Oxford due to a back problem with former Everton youngster Hope Akpan stepping in.
Manager Steve Evans plans to name a strong side as he attempts to repeat last season's cup run, which was only ended by a narrow 1-0 defeat at Manchester United in the fifth round.