Former Chelsea boss Antonio Conte feels his old side haven't yet figured out how to get the best out of Romelu Lukaku.
The Belgian returned to Stamford Bridge from Inter in the summer for a fee close to £100m.
Lukaku had just fired his side to the Serie A title, playing under Conte who had long wanted to work with the goal machine.
And the Italian reckons Thomas Tuchel hasn't yet worked out how to get the best from his big summer signing, who he rates as being nearly impossible to play against.
Conte said on Sky Italia: "If I had to face Lukaku I'd tell my players to keep him up the pitch away from the penalty area.
"He's always dangerous though, plus he's so good at giving assists to his team-mates, on an open pitch he has the speed to kill you.
"In my opinion Chelsea still haven't figured out how to get the best out of him because they've rotated a lot.
"If they can understand him they'll be the team to beat in the Premier League and the Champions League.
"These are the reasons I wanted him at Inter, just like I wanted him at Chelsea and at Juventus when he was very young."
