The 23-year-old was credited with his second assist of the season when Olivier Giroud opened the scoring five minutes into the encounter, adding to the six goals he has scored for Chelsea this season.
It is the first time Loftus-Cheek has started for Chelsea since early-January, as the England international had been suffering from a back injury.
But Sarri was delighted to see him back in the starting XI and singled out Loftus-Cheek for special praise due to the progress he has made.
While Eden Hazard has already predicted his team-mate will develop into one of the best in his position in England, the coach went one further.
"He did very well. He is improving in the last month," Sarri told BT Sport after Thursday's victory. "He has been able to train after the problem with the back. He had a wonderful match and I'm really happy he could play for 90 minutes.
"His potential as a player is very, very, high. Physically, technically and tactically he is improving, he can become one of the best midfielders not only in England but in Europe."
"We started very well. We wanted to start in this way," he said.
"We scored after five minutes which was a very difficult situation for the opponents. We played a wonderful first half and managed the game in the second half."
The Stamford Bridge side will find out their quarter-final and potential semi-final opponents when the draw is made on Friday. Sarri's outfit are in action again on Sunday when they visit Everton in the Premier League.