Hazard said this after him and the Frenchman combined well in Chelsea's 4-1 win over Cardiff on Saturday.
Chelsea not only kept pace against Cardiff but, through a 4-1 home victory against the Bluebirds , actually moved top of the table on goal difference. Chelsea are now second in the Premier League with 10 goals, and only defending champions Manchester City have more with 11.
Eden Hazard is now the top goal scorer in the Premier League.
Liverpool now top the table with four wins out of four, though Chelsea and Watford are also on 12 points after their flawless starts to the season.
Chelsea rarely relinquished control from that moment on, but it wasn't until substitute Willian won a penalty in the 80th that the Blues put the game beyond doubt.
"I think he can spend less energy than now, ' he said".
"If he wants to play for another season I think it's right he tries to play".
Sarri has been impressed with the Brazilian defender, as he said: "David has a big future here - he will be very useful for us". Leaving no scraps for the forwards to pick off behind a rigid defence, he made life very hard for Chelsea's attackers as they looked to produce clear-cut chances.
Chelsea FC will kick off their Europa League group stage campaign on Thursday night when they take on PAOK away from home. It's very hard. The gap last season was 30 points so I think to go above 30 points in one season is very, very hard. So I know that the matches after the break are very, very hard.
The hosts almost hit back immediately and in some style as backheels from Pedro Rodriguez and Olivier Giroud sent Mateo Kovavic clear on goal, but the Croatian was denied his first Chelsea goal by a fine save from Neil Etheridge.