Napoli attacker Dries Mertens has told Chelsea's players to always expect intensity from manager Maurizio Sarri.

Sarri guided Napoli to top three finishes in each of his three seasons in charge at the Studio San Paolo, taking the Neapolitan side closer than ever before to just a third Serve A title last season.

Mertens told The Times: “Sarri does not have an off button. I think he sleeps one hour a night and he is always thinking about football.

“Maybe because he had less time because he arrived late in the game and he is playing catch-up? I learnt a lot from him."

Mertens added: “The thing I loved most about him is that you feel you are playing with 12 not 11. He puts the line very high so the strikers feel the midfielders are close.

“I'm sure now Sarri is learning things about London. He knows so many facts, he's crazy but interesting."