Benitez has been using his contacts to understand his players and try to turn around the club's fortunes.
"I talked with him but also with Lille's coach Rudi Garcia that I know very well. I have a lot of information about Eden," he said.
"At Lille, he knew he was the key player and he played with that feeling 'I am the best, everything will be fine.' But when you go to a club like Chelsea, which plays in Premier League and Champions League, you always have to be at your best. That is something he will learn."