He scored 12 goals in all competitions, plus five assists last season.
Deulofeu told Sky Sports: "We spoke with the manager [Javi Gracia] at the beginning of the season and he said to me that I was going to play as a striker. Years before, I had been thinking that I wanted to play as a striker because you are nearer to the goal and you have more chances to score.
"Last season was really good for us, we can improve, of course and I can also improve my statistics. But I'm happy and I want to continue in that position.
"I had to adapt myself to Watford's style because there is a lot of long balls, direct and second balls. I had to adapt myself in that team and that type of football. In the last four or five months, I enjoyed playing with Troy [Deeney] and with people who go to the challenge and after, I can take some chances."