With the European transfer window not closing until August 31, Hazard has been linked with a summer move to Real Madrid.
The European champions have already brought goalkeeper Thibaut Courtois over from Chelsea, but Sarri was able to recruit Kepa Arrizabalaga for a world-record £71.6m before the Premier League window closed.
With Chelsea unable to replace Hazard, Sarri confirmed he expects the Belgian to remain at Stamford Bridge for the remainder of the campaign, and added that the playmaker is in line to start at Newcastle on Sunday – live on Sky Sports Premier League.
Sarri said: “Eden is ready for 50-60 minutes. I don’t know for 90 minutes, but he can start. I am happy with him. He wants to play. It’s the right way to think for him, but I have to think for everybody.
“I am the coach of a very good team. I am the coach of a very great club. It’s so important that such an important club cannot sell a very important player without the possibility to buy another very important player at the same level.
“I think Eden will stay with us for all of the season.”
Loftus-Cheek’s future remains uncertain after the England midfielder was left out of the squad to face Arsenal last weekend.
Sarri added: “I have spoken with him twice this week, after I spoke with the club. I think Loftus will remain with us, we can speak again about his situation, but I think only in December.”