The £50million man is hitting his stride at just the right time for Chelsea's bid to make amends for their failed defence of the Champions League by being crowned champions of the world.
"I have to speak to him in Spanish so he can tell me any jokes he has," interim manager Benitez said.
"When a striker is scoring, he is happy, happy. I've noticed the difference in him too.
"To be fair, the team is doing really well. I'm not surprised because they are all training very well. You don't have anyone who is lazy. Everyone is trying to do the right things."