Watford have doubts over Troy Deeney and Nathaniel Chalobah for the game with Huddersfield.
Deeney (hamstring) and Chalobah (knee) are training separately from the rest of the group and could join Sebastian Prodl, Daryl Janmaat and Tom Cleverley on the sidelines.
The Hornets are boosted, though, by the return of suspended duo Jose Holebas and Christian Kabasele.
Provisional squad: Foster, Cathcart, Kiko, Masina, Doucoure, Hughes, Capoue, Pereyra, Holebas, Kabasele, Deeney, Gray, Gomes, Mariappa, Britos, Sema, Navarro, Chalobah, Deulofeu, Wilmot, Success.
Ramadan Sobhi is in contention for his first start for Huddersfield.
The Egypt winger has been restricted to just six minutes of action this season following his summer switch from Stoke due to a knee injury.
Defenders Terence Kongolo (knee) and Tommy Smith could also be back in the squad after returning to full training.
Provisional squad: Lossl, Schindler, Jorgensen, Lowe, Kongolo, Durm, Billing, Hogg, Mooy, Hadergjonaj, Van La Parra, Mounie, Kachunga, Sobhi, Diakhaby, Depoitre, Hamer, Pritchard, Mbenza.