Sebastian Prodl, Craig Cathcart and Valon Behrami all face fitness test on minor injuries.
West Ham will assess Andy Carroll's groin problem ahead of the game.
Left-back Aaron Cresswell is fit after a hamstring niggle, and forward Andre Ayew is available for the first time since the Africa Cup of Nations.
Martin Fisher: "Watford's season effectively kicked off 41 minutes into their match against West Ham at the London Stadium in mid-September.
"Trailing 2-0, a deflected shot from Odion Ighalo reduced the arrears and proved the catalyst to a stunning revival.
"A 4-2 victory saw them soar out of the bottom three, early relegation fears were eased and they've not looked in serious trouble since.
"Improving on last season's finish of 13th looks within their reach, but that bid could be checked by a Hammers side that has been so impressive on the road since Christmas.
"Goals aplenty too along the way: 10 scored in victories at Swansea, Middlesbrough and Southampton."
Twitter: @mfisherfootball
Watford head coach Walter Mazzarri on the brilliant winning fightback against West Ham in September: "We cannot compare [Saturday's game] with that game.
"It was a long time ago. They had some problems in that period and we were coming from a particular period, too.
"We did a very good game after losing at the beginning. They are doing very well now."
West Ham manager Slaven Bilic on that reverse fixture: "We are a different team now. A lot of things have changed.
"When we played them in September we had a lot of players injured and we had to push players in who were not totally fit because we had no other options.
"We are in much better shape now."
Watford have had their wobble and, like West Ham, I think their relegation worries are over.
The Hornets mounted a stunning comeback from 2-0 down to beat the Hammers at the London Stadium earlier in the season, but this should be a more straightforward win for them.
Prediction: 2-0
Lawro's full predictions v Let It Shine judge Martin Kemp
Head-to-head
Watford
West Ham United
SAM (Sports Analytics Machine) is a super-computer created by @ProfIanMcHale at the University of Salford that is used to predict the outcome of football matches.

The Bridge of Carr at Carrbridge in the Cairngorms is also known as the coffin bridge due to its use by funeral parties to cross the Dulnain river.
The local community is to hold a programme of events from 19-21 May.
An exhibition of historic artefacts, a family ceilidh and live entertainment are planned.
The arching stone bridge was built between May and November 1717.
Among the reasons for its construction was the Dulnain had frequently been in spate in previous years.
In the 1690s, deaths in the area rose because of famine. Mourners were prevented from reaching funerals at the Church of Duthil when the river was swollen.
The bridge was built by John Niccelsone, a mason from Ballindaloch in Moray, at the behest of local landowner Brigadier-General Alexander Grant of Grant.
Its parapets and side walls were badly damaged in the 18th Century and again in a flood in 1829.
Watford are still without Nordin Amrabat and Christian Kabasele, who are sidelined with ankle and knee problems respectively.
[NEXT_CONCEPT]
Events are to be held to mark the 300th anniversary of the construction of what is thought to be the oldest bridge in the Highlands.