The on-loan Italian defender was shown his fifth booking of the season in Saturday's 2-0 win over Nottingham Forest and now serves an automatic one-match suspension against the Robins.
Victory may have taken the Hornets back into the top six in the Championship table but manager Gianfranco Zola has already stressed his intention to rotate over the hectic festive period.
"I have a big squad so I will use my numbers over the Christmas period because it is a tough time although we are equipped to do well," Zola told the club's official website.
Striker Fernando Forestieri (hamstring) is again not expected to be ready, along with defender Lloyd Doyley (calf).
Captain John Eustace and Nyron Nosworthy have both returned to training but are short of match fitness.
- Sports & Recreation
- Gianfranco Zola