Hazard came off the bench to provide the assist for Marcos Alonso’s late winner and Kovacic also played a key role as a substitute.
Sarri suggested that despite having to use both sparingly, he was happy to be able to employ them tactically against a waning opposition.
Sarri said to BBC Sport: “In this moment they are not able to play the full 90 minutes.
“Also, I think to play 25-30 mins when the intensity of the game is going down, is better.
“I think Mateo can become a great player.”
Kovacic moved to Stamford Bridge on-loan from Real Madrid as part of the deal which saw goalkeeper Thibaut Courtois head the other way, after he struggled to break in to the Champions League winners’ side.
The deal has been subject to much derision as Chelsea already have multiple high-class operators in the middle of the pitch, and detractors are critical of the Blues for once again signing established talent rather than bringing through academy players such as Ruben Loftus-Cheek into the first team.
Sarri brought in a central-midfielder of his own in Jorginho who has looked the part so far in a Chelsea shirt, and clearly the ex-Napoli boss has taken a liking to Kovacic too.
Last season’s top-scorer Hazard was a key part of the Belgium squad that were beaten by France in the World Cup semi-final this summer and has been linked with a move to Madrid this summer himself.
However, Sarri has been resolute that he is not going anywhere, and he will hope that Hazard can have a similar influence as his side travel to Newcastle next Sunday.
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