London (AFP) - Novak Djokovic says he still respects John McEnroe despite the retired American great comparing the Serb's slump to US golfer Tiger Woods' 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 former world No. 1 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 women's former world No. 1 Serena Williams would only rank 700th 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", McEnroe said: "If she had to just play the men's circuit, that would be an entirely different story".

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 via social media.

"Dear John, I adore and respect you but please please keep me out of your statements that are not factually based," she wrote in a tweet from her official Twitter account.

"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."