John McEnroe has always been controversial.

However, it hasn’t stopped the New Yorker becoming one of the most popular figures in tennis.

The 58-year-old won 77 career singles titles, including three Wimbledon titles and four US Open's.

He made it all the way to the Wimbledon semi-finals in 1977 after coming through the amateur qualifying pool, an achievement that has never been replicated.

Alongside his obvious talents on the tennis court, was his shunning of gentile conventions of the All England club.

McEnroe’s arguing with umpires and general on-court petulance made him something of a darling of the centre court crowd.

His enduring popularity earned him a job on the BBC’s Wimbledon coverage team.

Then in an interview with NPR, the New Yorker explained that if Serena Williams played on the men’s circuit instead of the women's, she would be ranked “like 700.”

His most recent comments regarding Novak Djokovic’s off-court issues with his family seems more than a little crass.

“The person that comes to mind with Novak is Tiger. He had issues and seemed to go off the rails," he said.

“That’s going to throw you. If you’re distracted, you’re not the same player.

“The person that comes to mind immediately with Novak is golfer Tiger Woods.

“He had the issues with his wife, he seemed to go completely off the rails and has never been even close to the same player.

“So we’re starting to say, ‘Wait a minute, is this possible with him?

“This isn’t a physical thing, this is a mental thing. There are definitely some issues.”

Regardless of Djokovic’s form this year, likening the 30-year-old's relationship issues to disgraced golfer Tiger Woods seems under the belt.

Novak Djokovic is through to the second round of Wimbledon after Slovak Martin Klizan, retired due to a calf injury after 48mins.