Ross Jenkins and Martin Taylor are hoping to be fit for the Hornets.
Midfielder Jenkins and centre-back Taylor, who played for Blues for six years before switching to Vicarage Road in 2010, missed the club's disappointing midweek Carling Cup exit at Bristol Rovers nursing knocks.
Striker Chris Iwelumo (hip/thigh) sat out at the Memorial Stadium having also missed last Saturday's goalless draw at Coventry and will continue to be monitored, although he stands a chance of being involved this time around.
Midfielder Prince Buaben made his Hornets debut as a 64th-minute substitute against Rovers but remains short of match fitness and will again be competing for a place among Sean Dyche's substitutes.
Stephen McGinn (knee) continues to be a long-term absentee while young defender Adam Thompson has joined Brentford on an initial month's loan but would not have been involved against Chris Hughton's side.
Birmingham's Liam Ridgewell is expected to return for the trip.
The defender missed last weekend's 3-1 defeat at Middlesbrough as well as Thursday's memorable 3-0 second-leg victory over CD Nacional having had stitches in a shin wound sustained in the first encounter.
Hughton, who picked up no fresh injuries on Thursday, will again check on midfielder Morgaro Gomis and defender Scott Dann, who have also missed the last few games due to minor knocks.
New loan signing Guirane N'Daw is set to be in contention for his debut providing the relevant paperwork is cleared.
Young midfielder Jordon Mutch is out for up to three months with a broken ankle, but there does seem to be light at the end of the tunnel for strikers Cameron Jerome (heel), Marlon King (knee) and Nikola Zigic (groin), who are yet to feature this season.
Hughton said: "We have some players who are not that far away, Cameron Jerome is very close as is Marlon King. Nikola Zigic is not too far away, perhaps maybe a week after the international break."