The Third Round tie represents a reunion for Silva and the Hornets.
“We have to go step by step,” Silva said at his media conference on Thursday. “But yes, we want to go as far as we can and the furthest is the last game of the competition.
“Two seasons ago we reached the Quarter-Finals. Last season, we reached the Carabao Cup Semi-Finals too. Of course, we are not in the Carabao Cup anymore and I told the players in today's session that (we need) top ambition in this competition.
“I think all clubs, they should look at the FA Cup in the way it deserves because it’s a historic one. It’s a competition that, in this country, everybody loves, and the last day of the competition, the Final, is something unbelievable.
“If you can participate as a football player or as a manager, I think it’s one of the greatest moments that you can have in this country.
“Of course, we have to go game by game. Now it’s Watford and we want to go in with full ambition that we can beat them to be in the next round.”
On facing his old club, Silva also said: “The impact was incredible straight away but after a bad spell in terms of results they changed things. I still have connections with some of the players and some of the staff, and it's a good feeling when you have an impact on the people.
“One of the good examples is the manager that I'm going to face tomorrow. First of all, he's a great guy. I'm really pleased to see him doing well as manager. Tomorrow, let's hope we can beat them, but I’ll always be supporting him and wishing him the best.
“We analysed them. We played against them last pre-season as well, although they're slightly different now.
“If you want to analyse and give feedback to our players, it's not going to be easy to give just one because they have been changing formation between games. But we're going to be aware of everything.”