The Belgian has missed Chelsea's last three games due to a back injury.
Speaking before Chelsea's clash with Palace, Sarri confirmed Hazard will play. But the Italian was not sure whether he would be able to cope with starting the match.
Sarri said: "Yesterday, he (Hazard) had a large part of the training with the team but maybe he will not be ready to play for 90 minutes at the moment - because it was his first training for the past two weeks.
"Probably he will be able to play for 40-45 minutes, so for us it is important."
Asked if Hazard would start or come on later, Sarri said: "I don't know, I want to speak with him first."