After losing three consecutive league games, Silva’s men are now back on track after back-to-back victories over West Ham United and Newcastle.
The Hornets are now eighth in the Premier League table and full of confidence having already proved more than a match for Arsenal this season.
United laboured to a 1-0 win over Brighton on Saturday and Silva is adamant his troops can get the job done at Vicarage Road.
He told the Watford Observer: “We will do our best tomorrow and I am sure we will compete. With the result we will see, but we will compete.
“We did our work and analysed the Man United team and they are strong this season. We looked at some moments in the game and it is important we can compete tomorrow and play with confidence.
“I am happy with how we have worked since the first day to compete really hard during the match. Every game we compete to win and this is our way.”