Italian Sarri then revealed he told Hazard on Friday that he can boost his goal return considerably - by focusing on operating exclusively in the final third.
"My type of football has always been to have the ball, to play with the ball, create chances".
"I told him... for me you can score 40 goals but you have to spend less energy".
Worryingly for the rest of the Premier League, Sarri believes Hazard can get even better if he stays further forward and wastes less time in his own half.
The French World Cup victor proved the ideal foil for Belgian star Eden Hazard and the pair combined to drag the home side back from a goal down in the first half.
"We did not play very well in the first 15 minutes", Sarri said.
He also said manager Maurizio Sarri, just wants his players to possess the ball and play good passes.
Cardiff took the lead thanks to a risky free kick and anxious Chelsea's defence with set-pieces throughout the match.
Sarri admitted he would rotate the two strikers according to the qualities of Chelsea's opposition: "I watched Cardiff four times and thought Giroud was right for this match".
Chelsea have enjoyed a stellar start to the new Premier League season, and they'll look to keep their momentum going on Saturday.
"At the moment I can answer Manchester City or Liverpool".
Asked if he would revise that view after Chelsea's latest win, Sarri replied: "No. I am talking about a week ago". "I think that he can spend less energy than now at 50 or 60 metres to the opposite goal".
Liverpool and Chelsea continued their flawless starts to the Premier League season on Saturday, and together have done something England have not seen in over a century.
"In the second half, maybe our ambition went a little bit down", Mourinho said. But our target is this.
"The last time I have spoken with him, he told me that he wants to play for another season".
Morata was an unused substitute as Eden Hazard's hat trick propelled Chelsea to a 4-1 victory at Stamford Bridge, with Giroud impressing despite failing to score.
"I have to organise better the defensive phase and the players have to understand that".
Eden Hazard scored his second Premier League hat-trick, in the win over Cardiff.
"Mentally the match after the break is always very hard". Joe (Bennett) should have won that tackle, and Bobby Reid, it's never a free-kick.
"I don't know now the situation".