Watford:
The Hornets sit in eighth place in the Premier League after their 3-0 victory over Newcastle at the weekend and will be boosted by the return of captain Troy Deeney, who has completed a three-match suspension.
Defender Miguel Britos is a doubt, while Craig Cathcart (knee), Younes Kaboul (hamstring), Nathaniel Chalobah (knee) and Isaac Success (knee) all remain sidelined.
Manchester United:
Striker Romelu Lukaku will be available for Tuesday's encounter after a three-man panel of former officials decided not to take action for his kick out at Gaeten Bong during the Red Devils' game against Brighton on Saturday.
However, Zlatan Ibrahimovic could make his first start in a United shirt since returning from injury to replace the out-of-form Lukaku, who has scored just once in his last 10 games.
Recent form:
Possible lineups:
Watford: Gomes, Mariappa, Kabasele, Prodl, Femenia, Hughes, Doucoure, Cleverley, Zeegelaar, Richarlison, Gray.
Manchester United: De Gea; Valencia, Smalling, Lindelof, Young; Matic, Pogba; Martial, Fellaini, Rashford; Ibrahimovic.