Story highlights Hazard has ability to be world's best, says Michael Ballack

But the former Chelsea star questions Hazard's desire

He says he should learn from world-class Luka Modric

(CNN) Belgian forward Eden Hazard could be as good as Lionel Messi and Cristiano Ronaldo if he changes his attitude, according to former Chelsea midfielder Michael Ballack.

The attacker has been pivotal to Chelsea's unbeaten start to the season, scoring six league goals in his first seven games, but has often experienced dips in form throughout his stay in London.

Ballack wants to see more consistency and a better work ethic from the 27-year-old but questions whether Hazard has the drive to be considered amongst the best in the world.

"You have to ask him if he wants to compete on that level because he has the ability," Ballack told CNN Sport.

"Sometimes he seems a bit happy with what he has, with the environment at Chelsea. He's a great player, he shines a lot, he can switch on his engine when he wants."

Eden Hazard celebrates after scoring his wonder goal against Liverpool in the League Cup.

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