Bristol Rovers manager Paul Buckle could again be without Joe Anyinsah for the game.
The striker missed the goalless draw with Macclesfield at the weekend after sustaining a hamstring injury during the 2-1 win over Northampton and Rovers will wait until the last minute before naming the former Charlton player in their squad.
Chris Zebroski is likely to retain his place in attack if Anyinsah fails to recover in time.
Forward Eliot Richards and midfielder Wayne Brown were both second-half substitutes at Moss Rose and may be given opportunities against the Hornets.
Former Pirates player boss Stuart Campbell has yet to play this season and will continue to occupy the sidelines with a hamstring complaint, while Gary Sawyer is still recovering from a hernia operation.
Ross Jenkins and Martin Taylor face late fitness tests for Watford.
Central midfielder Jenkins and centre-back Taylor both emerged from Saturday's goalless draw at Coventry nursing knocks and will be assessed as late as possible.
Striker Chris Iwelumo missed the encounter altogether due to a hip/thigh problem and he will again sit out at the Memorial Stadium as Watford's medical team look to get the striker fully fit, after a pre-season hampered by minor hamstring trouble.
Young striker Gavin Massey was also unavailable to face the Sky Blues having gone down with illness but he has a clean bill of health this time around.
The initial scheduled meeting between Watford and Bristol Rovers earlier this month was postponed at the request of police following the riots that took place in the south-west city, mirroring those across England.
