John McEnroe is no stranger to recent controversies having stated that Serena Williams would only rank 700 in the world if she played on the men's tour.

Now, he has shifted his attention to Novak Djokovic, who he claimed his latest difficulty on the court could have been caused by off-court issues with the family. But the Serbian is not taking John seriously.

Djokovic says he still respects McEnroe despite the American comparing the Serb's slump to Tiger Woods's similar decline and hinting at troubles in the three-time Wimbledon champion's private life.

McEnroe caused a stir by claiming that Djokovic's recent difficulties on the court, which have seen him lose possession of all four Grand Slam titles, could have been caused by "off-court issues with the family".

"The person that comes to mind immediately is Tiger Woods," said McEnroe in reference to the golf superstar whose life and career imploded after a series of extra-marital affairs were revealed.

But Djokovic, the winner of 12 Grand Slam titles, shrugged off McEnroe's comments.

"He's very well known for his kind of bold comments and not really caring too much about being politically correct but saying whatever is on his mind," said 30-year-old Djokovic.

"That's all I can say. I really don't take anything personal. I always got along very well with John.

"You know, I guess whether that's his opinion or criticism or something else, I'm not really sure. But in the end of the day, I respect everything he says."

McEnroe is no stranger to recent controversies having stated that Serena Williams would only rank 700 in the world if she played on the men's tour.

While describing 23-time major winner Williams as the "best female player ever -- no question", he put her around 700 compared to men.

"If she had to just play the men's circuit that would be an entirely different story".

Long-time world number one Williams, who won this year's Australian Open while pregnant, is taking the rest of the year off to have her first child.

She hit back at McEnroe.

"Dear John, I adore and respect you but please please keep me out of your statements that are not factually based," she wrote on Twitter.

"I've never played anyone ranked 'there' nor do I have time. Respect me and my privacy as I'm trying to have a baby. Good day sir."