Hazard, with 19 goals this season, came on in the 61st minute as Chelsea fought from a goal down to draw 1-1 in their Europa League semi-final first leg.
“For a player that has 70 matches in a season, starting him from the bench is a normal reaction,” manager Sarri said.
“We have to play again in 62 hours.”
The Italian explained that he did not inform Hazard, rumoured to be leaving Stamford Bridge in the summer, of his decision before kick-off.
“I don’t speak with the players that I want to put on the bench,” he added.
“He is a player, so I have to do it otherwise I have to speak to everyone. He was a normal way, joking as usual. He knows the truth very well.”