Hazard's scintillating hat-trick dominated Chelsea's 4-1 win over Cardiff on Saturday.
The win pushed the Blues to the top of the table and extended their perfect start to the campaign to five matches.
And former Napoli manager Sarri believes Hazard has enough of an eye for goal to outscore goal-scoring rivals Harry Kane and Mohamed Salah.
Asked if Hazard can win the Golden Boot, Sarri replied: "I think so. We have spoken and I told him he can score 40 goals.
"He has to improve some things, but he can do it."
Asked if Hazard believes Sarri's claim he can reach 40 goals, Sarri said: "If you have seen Saturday's match, then I think so!"
The Belgian ace has now scored five goals and registered two assists in three starts.