The Chelsea forward has made a blistering start to the season, with eight goals in ten appearances in all competitions so far this season.
But Sarri has urged his star man to improve if he wants to make the step up and join the elite.
He said: “Hazard is immense and I don’t think even he knows how much he can still improve.
“I said he could end up in the tight circle of the best three or four players in the world.
“The problem is he plays to enjoy himself and at times doesn’t realise the importance of moving from fun to reaping the rewards.”
Hazard has never reached 20 goals in a single season since moving to stamford Bridge and Sarri believes the 27-year-old must adapt his game to become more prolific.
The Blues boss added: “At the end of the day, you’ve got to get the fruits of your labour.
“Hazard’s approach is a positive, but it can become a potential limitation too.
“He needs to lift his head up, look around and realise there’s a whole world in front of him that he can dictate with his feet for the good of the team and not just the individual.”
Sarri’s comments were made just after Hazard admitted he would love to one day work with Manchester United boss Jose Mourinho again.
The pair won the Premier League and the League Cup together in 2014-15, when Hazard racked up 19 goals – his best ever return since moving to England.
On his ex-boss, he said: “If I’m now asked one coach with whom I want to work again, then I say: Mourinho.”
He continued: “If you win, Mourinho is the best coach you can imagine. Then he is a friend of yours – you can do whatever you want.
“Want one day off? He gives you two. If everything goes well, Mourinho will experience football like me: with ease.
“Even his own image of an extremely defensive coach was not too bad.
“He is far from adventurous like [Pep] Guardiola, but the year in which we became champions, we scored a lot of goals and played good games.
“I do not regret many things in my career, but that I have not been able to work with Mourinho at Chelsea anymore [is one].”