Captain Michael Dawson was forced off in the second-half of Saturday’s 2-0 FA Cup third round win over Swansea City at the KCOM Stadium with a shoulder injury.
The former Tottenham Hotspur centre-back is now a major doubt for the trip to Old Trafford and that would leave Silva massively short in the defensive department.
Harry Maguire missed the clash with the Swans and his participation still remains uncertain, with the Tigers’ boss to make a late call on his involvement.
Curtis Davies is definitely ruled out as he continues to recover from a hamstring problem and that could force Tuesday’s visitors into putting three midfielders into their defence.
Jake Livermore, David Meyler and Tom Huddlestone were all shipped into the backline for the FA Cup victory and the trio could be asked to play in those positions again.
Abel Hernandez may be fit enough to start after making a goal-scoring return to action from the bench on Saturday, but again Silva will make a late call on his involvement.
Watford boss Javi Gracia does not think Abdoulaye Doucoure's form will be affected by his omission from France's latest squad.