Femenia, who is recovering from a hamstring issue, has trained this week but manager Nigel Pearson believes the visit of Spurs will come too soon for the winger.
Will Hughes has also returned to training, but will not be in contention, while Sebastian Prodl (shin), Daryl Janmaat (knee), Danny Welbeck (hamstring) and Tom Cleverley (foot) remain sidelined. Ignacio Pussetto is set to make his debut. Christian Kabasele returns from suspension.
New Tottenham signing Gedson Fernandes will be involved.
The Benfica midfielder has joined on an 18-month loan this week and could be on the bench while Christian Eriksen will start.
Watford provisional squad: Foster, Cathcart, Hughes, Doucoure, Capoue, Deulofeu, Kabasele, Deeney, Sarr, Gomes, Dawson, Masina, Foulquier, Chalobah, Pussetto, Pereyra, Quina, Gray, Success.
Tottenham provisional squad: Gazzaniga, Vorm, Aurier, Walker-Peters, Tanganga, Alderweireld, Vertonghen, Sanchez, Rose, Dier, Winks, Wanyama, Fernandes, Skipp, Eriksen, Lo Celso, Alli, Lamela, Moura, Son.