Maurizio Sarri believes Ross Barkley has potential to be one of Europe's best midfielders after initially struggling under the Italian.
Barkley is in contention to play against former club Everton for the first time on Sunday, 10 months after moving to Stamford Bridge from the Toffees.
The 24-year-old has thrived under Sarri, scoring three goals in his last five games and earning an England recall. The Chelsea boss predicts he can get even better.
"He is a complete player," Sarri said. "He is fast. Technically he's very good. He's improving in moving the ball, mentally quicker. And he's improving tactically.
"I think he's on the way to becoming a very important midfielder, not only in England."
Sarri's first impressions were not quite so glowing. Barkley arrived at Chelsea carrying a hamstring injury and played just four times under Antonio Conte, who Sarri succeeded in July.
"At the beginning he was in trouble," the 59-year-old former Napoli boss said. "In the first month he was in trouble. Then he started to improve in every training, in every match."
Barkley may be facing his boyhood club, but Sarri likes to take the emotion out of such occasions - and the Former Everton man may not start.
Sarri added: "In every match I have a player who is an ex. I want to choose for another way, not for this kind of thinking."
Alvaro Morata, David Luiz, Antonio Rudiger and Marcos Alonso were all rested from Thursday's Europa League trip to BATE Borisov in Belarus and could return to Chelsea's starting line-up.
N'Golo Kante is also likely to feature, having been a late call-up to the trip to deputise for Cesc Fabregas, who called in sick. Kante did not feature.
Fabregas and Ruben Loftus-Cheek, who has a minor back problem, are the only doubts.
