Doucoure joined the Hornets from Rennes in the winter window of 2016 but was initially loaned out to Granada in Spain.
The French midfielder had to wait for his chance at Vicarage Road and forced his way into the side under Walter Mazzarri last year and has been a regular for Marco Silva this season.
The 24-year-old impressed in the 2-0 win at Southampton last time out with the opening goal and has lofty ambitions for the campaign ahead.
He told the Hertfordshire Mercury: “I’m happy and I’ve worked for that [chance to play regularly]. I want to be, and I said before the season, I want to be one of the best midfielders in the league.
“In the team I want to be a leader and after Southampton I’m happy and [we] have plenty to work on. We’ll see at the end of the season where I am.”
He added: “In the Premier League nobody knows me, I have to work and be one of the best. I have to show more performances like Southampton.
“I just want to work and to win the games – which is important for the team. After the individual players can come out.”
Richarlison has revealed how he heard of Marco Silva's sacking and admits the Watford squad can't explain their mid-season dip in form.