Success has impressed early in the season since joining the Hornets over the summer, although he's been largely used as a substitute so far.
He was handed an opportunity from the start in Sunday's 1-0 win at Middlesbrough but struggled to get into the game, according to head coach Mazzarri, who says the Nigerian will need to be given time to settle.
Mazzarri said: "He [Success] played well, as did the whole team, but he did much better in the other games when he came on from the bench.
"It’s not easy to start a game. It’s completely different but if he gets his full condition then he also needs to learn some things and he will be a great player."
The 20-year-old will hope to earn another start for Watford this weekend when Mazzarri's side travel to take on Swansea City.