Watford will be without winger Andros Townsend.
Townsend made his debut at Cardiff last weekend after signing on loan from Tottenham but cannot play in the Cup having featured for Spurs in the third round.
Fellow midfielder Josh Walker is also cup-tied having played for Stevenage earlier in the competition but on-loan Aston Villa striker Andreas Weimann can play.
Captain John Eustace is "touch and go" to return from the calf injury he sustained against Portsmouth on New Year's Day.
Scottish winger Don Cowie is still out with a thigh strain as the Hornets look to return to winning ways after the defeat in Wales ended a run of seven straight victories.
Brighton will check on Radostin Kishishev.
The Bulgarian was substituted during Tuesday night's win over Colchester with a back spasm and will not be risked if he is not 100% fit.
Fellow midfielder Liam Bridcutt suffered a calf injury against the Us but he is already back in training and available for selection.
But winger Craig Noone is cup-tied having played in the competition for previous club Plymouth and Alan Navarro (knee), Jim McNulty (ankle) and Jamie Smith (foot) are still sidelined.
Back-up goalkeeper Peter Brezovan has played in every round so far and will come back in for Casper Ankergen while Tommy Elphick and Ashley Barnes could also get run-outs.