The headlines won't tell the whole full story tomorrow, with a scoreline that flattered the hosts, but it was a tough lesson to learn for the Premier League newcomers.
The Belgium worldwide surged through the defence before finishing powerfully in the 37th minute at Stamford Bridge to cancel out Sol Bamba's surprise opener from winless Cardiff.
But Sarri is looking for better things from his squad.
And Chelsea fans spotted the reaction Hazard got about his performance from club legend Gianfranco Zola - who is Sarri's assistant.
'When Alvaro is playing it is completely different he is a different type of player both are quality so we are happy to have good strikers'.
Sarri established a reputation in Italy as a pure coach who is obsessed with thinking about football and preparing meticulously for his opponents, but the vibe he gives off is not as intense as the one that surrounded Antonio Conte during his two years at Cobham.
Players and other influential figures at the club had exhausted of Antonio Conte's intensity and sniping at a lack of transfer activity.
The Real Madrid loanee was forced off after the half-time break of Chelsea's win against Cardiff. Winger Willian, meanwhile, was wanted by Barcelona.
The Blues are now on top of the Premier League table with 15 points.
It's been a rough beginning for Cardiff, as they've only managed to secure two points in their first four games.
Sarri has enjoyed a fast start in his initial campaign in England as the Blues recorded four wins on-the-trot in as many Premier League games.
'We know especially after the break it's hard to play a good game because we are all a bit exhausted but we got an important three points today.
On paper, this game looks like a straightforward win for Chelsea.
Terry turned down a lucrative one-year contract from Spartak Moscow this week after a late change of heart, but has been open in his desire to play on for one more season and has been linked with a return to Aston Villa.
City and Chelsea await in Liverpool's next three league games and secured comfortable home victories to boost their own title chances.