Novak Djokovic has questioned why John McEnroe made claims about his private life and likened his dip in form to the problems Tiger Woods experienced after the American golfer's infidelities were revealed.
Former Wimbledon champion McEnroe, now an in-demand tennis commentator, said on the BBC this week that Djokovic has "off-court issues with the family".
McEnroe added: "The person that comes to mind immediately with Novak is not a tennis player, it's actually a golfer: Tiger Woods.
"Woods had the issues with his wife and then he seemed to go completely off the rails and has never been even close to being the same player. So we're starting to say: 'Wait a minute, is this possible with him, Djokovic?'"
Although Djokovic has admitted over the past year he has been dealing with personal issues away from tennis, he was surprised by McEnroe relating his situation to the crisis Woods faced in 2009 when it was alleged he had several extramarital affairs.
Woods and wife Ellen Nordegren divorced months after the claims were made. The 14-time major winner has not won one of golf's big four tournaments since the scandal.
Djokovic does not currently hold a grand slam, having held all four before coming to Wimbledon last year.
Asked about McEnroe's comments, Djokovic said the American had the right to say what he wanted, but added: "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."
Djokovic and wife Jelena married in 2014 and are expecting their second child.
As for whether the comments from McEnroe were justified, Djokovic said: "He has his right to say the things he wants to say. I don't necessarily need to agree with that. But it's his right.
"So I don't know where was the basis, and he was just maybe making a comparison. I'm not really sure.
"When I was warming up for my first match on the Centre Court, he was giving an intro, talking to the camera, and I served and the serve went straight at him as I was playing. I don't know.
Maybe it's because of that. Maybe he thought it wasn't a joke and I was joking, I was trying to hit him.
"I don't know. I take it very lightly. I don't think there was any kind of really wrong intention from his side towards me."
Wimbledon's blazing afternoon sun on Thursday was no hindrance to Djokovic as he brushed aside Adam Pavlasek on Court One, a 6-2 6-2 6-1 win taking just one hour and 33 minutes.
Coach Andre Agassi emerged to watch the match without a hat, and had to improvise by draping what looked like a tracksuit top over his bald head to stave off the threat of sunburn.
He sat in a box at courtside alongside a short-term addition to Djokovic's team, the former top-10 player Mario Ancic, whose regular day job is as an investment banker on Wall Street.
Djokovic at one stage took issue with comments he heard coming from the stands, but denied it was Pavlasek's entourage that had annoyed him.
"I just don't like when somebody comes to the stands with intention to just provoke and intentionally cheer against and just say certain things that are not right when you're close picking up the towel," Djokovic said.
"I have no problem to confront anyone because I will not allow anyone to do something that is not right."