"I think (Loftus-Cheek) can become one of the best midfielders, not only in England but in Europe," Sarri told BT Sport after his team advanced to the quarter-finals with an 8-0 aggregate scoreline.
"His potential as a player is very, very, high. Physically, technically and tactically he is improving."
A persistent back injury has limited Loftus-Cheek's playing time this season and Sarri was pleased to see the midfielder play the entire match.
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"I'm really happy he could play for 90 minutes," Sarri added. "He did very well. He's improving in the last month and has been able to train after the problem with the back."
Chelsea, who are currently sixth in English top flight, travel to Everton in the Premier League on Sunday.
(Reporting by Rohith Nair in Bengaluru, Editing by Simon Jennings)
