Teenage midfielder Jenkins is continuing his recovery from a back injury and defender DeMerit remains sidelined after his recent eye surgery.
Boss Malky Mackay says the duo are "weeks rather than days away", so he will probably stick with the team which thumped Scunthorpe 3-0 last Saturday.
Heidar Helguson keeps his place in attack after scoring twice against the Iron to take his tally to five goals in four appearances since rejoining the Hornets on loan from QPR.
Back-up goalkeeper Richard Lee will be on the bench as cover for Scott Loach after recovering from the knee injury which sidelined him for five games.
