Hazard was singled out by team-mates after the 3-2 home win over Shakhtar for his lack of work-rate.
Benitez said: "He has to adapt to the tempo of the Premier League. It's not the same as France where he was the main man. 'Here in the Premier League you have to be at your best all the time or you will not be able to make the difference in matches. He's doing well, but he could do better."