The Belgium winger impressed during his first season at Stamford Bridge following his move from Lille in June 2012, and has kicked on in his second campaign at the London club.
Hazard has scored 11 so far this season and Mourinho has seen the 23-year-old move to another level during his second tenure with the Premier League high-fliers.
He told the London Evening Standard: "Eden can become one of the best players in the world. Now he sees his football and profession with different eyes.
"He understood how there is a gap between the talent and the performance and a gap between the occasional performance and the permanent stability at a high level. He now understands how he can fill this gap.
"He trains much better, he concentrates much better. Tactically, he has had a big evolution. He understands how to put his qualities on the surface of the team. He understands the best way to hide his weaknesses.
"He is 23 and now in his second season in England after an experience in France. He is playing in a Chelsea side trying to win the Premier League, also the Champions League, and is going to the World Cup with Belgium. He has in his hands all the tools to fill these gaps.
"Everyone knows he is a talented player, that he was that when he arrived here. But now he is trying to go to a different level, we are helping him and he is doing it step by step. Hopefully, the big talent can transform himself into the big player."
