The 26-year-old has made 154 appearances for Chelsea so far, keeping 58 clean sheets along the way.
Courtois, who has been heavily linked with a move to Real Madrid, was handed an extended holiday after helping Belgium to a third-place finish at the World Cup.
"I want to hear from [Thibaut] Courtois", he said following Chelsea's 2-0 defeat to Manchester City.
Chelsea's eagerness to halt Real Madrid's efforts to sign Hazard may lead to him being offered the chance to become club Blues captain, yet persuading Courtois and Willian to stay will be a tough task.
"With the players we've got and ability that we've got, we just want to keep on working hard together to make the club great and keep doing well", he said.
Reina, who played for Chelsea's Premier League rivals Liverpool between 2005 and 2013, is not guaranteed first-team football at San Siro, with Gigio Donnarumma expected to start the new season as first choice.
Sarri has been in charge at Stamford Bridge for just three weeks, following Antonio Conte's sacking, but the Italian is already preparing for his first league match in charge against Huddersfield this weekend.
Chelsea have never entertained any talks with Real about Hazard and the Belgian was clear from the outset that he would not agitate for a move.
Riyad Mahrez to Manchester City from Leicester. I want them to stay, because we have top players with the confidence.
Let us know in the comments. "I can't say much about it now either".
"I can not say much, I am not thinking about that, I am calm and becoming anxious would not help". I've watched clips of his Napoli team to see the way they played.
The Italy global, who was born in Brazil, was transferred to the London club from Napoli in a deal worth almost £60million this summer.