John McEnroe surprised BBC Wimbledon viewers when he compared Novak Djokovic with troubled golfer Tiger Woods.
Speaking about Djokovic's period of poor form, McEnroe compared the former Wimbledon champion with Woods, who in the past has had a high-profile divorce, been arrested, and suffered problems with prescription medication.
McEnroe claimed Djokovic "had some off-court issues with the family," adding: "That's going to throw you."
"If you're distracted you're not the same player," he said.
"When he [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]?'"
Former world number one Djokovic has suffered with his form in the last year - after completing a career Grand Slam last year, he started to lose matches and momentum.
He is married to Jelena, 31. They have a son together and she is expecting their second child.
In 2009, Woods crashed his SUV into a tree and a fire hydrant outside his Florida home. Just months later he was divorced after reports of extra-martial affairs surfaced.
McEnroe added: "I think there's a big difference, one is the age, but two the health. I think this (Djokovic's form) isn't a physical thing, this is more a mental thing."
The commentator also sparked controversy recently when he said that 23-time Grand Slam winner Serena Williams would be ranked around 700 if she competed in the men's game.