Eden Hazard scored a goal-of-the-season contender to defeat Liverpool in the Carabao Cup, but Gianfranco Zola thinks he can still improve.
The Belgian came off the bench at Anfield to score the winner against their Premier League rivals.
Daniel Sturridge netted the opener two minutes after Hazard arrived on the pitch, Emerson equalised, before the Belgian completed the turnaround thanks to a sublime solo effort.
Despite his virtuoso goal, Zola believes the Chelsea forward can still become a better footballer.
"He [Hazard] is not only one of the best in the Premier League, if not the best, but he's one of the best in Europe and the world.
"Eden's growing fast, he's growing fast in maturity, in choices he's making on the pitch and I think, in my opinion, we haven't seen the best yet."
Asked if there is more to come from Hazard, Zola said: "I believe so because he has an unbelievable potential inside him and he's getting to the point when he's using it at the right moment and that's something remarkable.
Hazard defeated a number of Liverpool defenders before firing an unstoppable shot beyond Simon Mignolet to earn the victory and Zola's praise.
"I think it was a fantastic goal, especially not only for the beauty of it but for the moment he scored and he was all on his own, I guess - four defenders - and it was an unbelievable goal."
The former Lille forward started on the bench but it was always part of Maurizio Sarri's plan to introduce him in the second half at Anfield.
"He was planned to have a change around 50 minutes with Willian because also Willian has played a lot of games."
Chelsea will face Liverpool once again on Saturday in the Premier League but Zola does not think Wednesday's result will influence the outcome at the weekend.
"To be fair it was a close game because they were doing well. They could have won, in the end we won, but fair to say they are a brilliant team.
"Not at all, Saturday is going to be a completely new game, very exciting game and I hope it is going to be as beautiful as today. Both teams wanted it but Saturday is going to be different."