NEW YORK • John McEnroe has told Nick Kyrgios to quit professional tennis if his heart is not in it.

Commentating on American television, the tennis legend was scathing of the controversial Australian's demeanour before he retired from his third-round US Open match against Illya Marchenko with a hip flexor injury on Saturday. Kyrgios was trailing 6-4, 4-6, 1-6 when he called it quits.

The 14th seed complained of the injury during his first two matches and said he felt like he'd been "hit by a bus" at one point during the defeat.

"I can't move. I can't turn, mate," he said to his courtside trainer. "What's the f***ing point?"

McEnroe has been critical and complimentary of Kyrgios in equal measure since the 21-year-old's emergence as one of tennis' hottest prospects.

But his latest attack was particularly harsh, given Kyrgios' obvious injury concerns.

"Nick Kyrgios, if you don't want to be a professional tennis player, do something else," McEnroe said. "He's hurt because he's not training enough."

Despite McEnroe's criticism, Kyrgios attributed the injury to training and playing overload.

"It's the whole year leading up to it with the whole schedule," he said. "I've got to take more time and be more diligent with gym and everything so this doesn't happen to me."

But, despite the setback, he is set to climb to a career-high No. 15 in the world rankings.

THE GUARDIAN