The Icelandic striker missed Monday night's 3-1 win over QPR due to the terms of his loan deal from the west London club.
Nathan Ellington, who was handed a rare start against Rangers, is likely to find himself on the bench again with Helguson partnering Danny Graham in attack.
Boss Malky Mackay will hand a late fitness check to Henri Lansbury after the on-loan Arsenal midfielder sat out on Monday with a hip injury.
Club captain Jay DeMerit could also return to the starting line-up for the first time since August.
The American defender came on at half-time against Rangers after more than three months out recovering from eye surgery.
Jake Buxton could return to the Derby squad for the trip to Watford.
A string of injuries have kept the centre-half out since the end of August but he played 80 minutes for the reserves this week.
Boss Nigel Clough, who expects to still be without Shaun Barker (thigh) and has doubts over the fitness of Dean Leacock (hamstrings) and Miles Addison (foot), said: "If Jake suffers no reaction, he will be in the squad. He will probably be on the bench to cover us as I think we are going to be very short in the centre-half department."
Leacock started the goalless draw at Preston on Tuesday night but was forced off 10 minutes into the second half as full-backs Jay McEveley and Paul Connolly finished the game as the centre-back pairing.
Chris Porter made his first competitive appearance since the beginning of March as a second-half substitute at Deepdale following a troublesome hip problem.
The striker, along with fellow forward Steve Davies (hamstring), midfielder Ben Pringle (knee) and goalkeeper Saul Deeney (ankle), also featured for the reserves this week and could be included in the squad once more.
Sporting Life