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.”
Barkley did not play for Everton in the last seven months of his spell due to a hamstring problem and moved in a cut-price £15million deal, with his contract winding down.
Barkley anticipates facing some hostility from Everton’s visiting supporters, after moving on following 13 years at Goodison Park.
“I don’t think it (the reception) will be the best,” he said in the London Evening Standard.
“I’m not nervous, I’m excited to play against my former club and team-mates – I understand how some of them play, so that could be an advantage for me.
“On the day I might get a few nerves as it will feel a bit strange. I’m looking forward to catching up with some of the staff there who I used to get on really well with.”
This post was last modified on 10/11/2018