Hazard struck a hat-trick in victory over Newcastle United on Saturday.
Leekens told the London Evening Standard: “While with Lille, Hazard was the best player in France playing at 70-80% - now he is playing at 100%. Perhaps he was guilty of taking training too easily sometimes in the past, but he is working hard in training now and Jose Mourinho has raised the bar for him.
“The Chelsea manager has not only demanded Hazard scores more goals and produces more assists, but also that he works hard defensively and takes responsibility. He has responded and I think he has been accepted by the other Chelsea players.
“The World Cup is the right moment to show himself, he will be excellent. His performances against the likes of Manchester City and Liverpool have shown he is ready for the biggest teams in the World Cup.
“He has the talent to be considered on the same level as Ronaldo and Messi - after the World Cup, maybe people will stop comparing him to those players and appreciate him for the player he has become.”