Novak Djokovic stands on the verge of holding all four Grand Slam titles for the second time in his career and should he do it by winning the French Open, it would surpass anything Rafael Nadal or Roger Federer have achieved, said Mats Wilander.
Three years ago Djokovic became the first man since Australian great Rod Laver in 1969 to hold all four Grand Slams simultaneously when he beat Andy Murray to win the French Open.
A career slump followed but the Serb rebounded last year to win Wimbledon and the U.S. Open and this year took his Grand Slam total to 15 after holding aloft the Australian Open trophy for a seventh time.
Now he has the chance to win four in a row again and seven-time Grand Slam champion Wilander believes victory in Paris would pave the way to surpass both Federer (20) and Nadal (17) in Grand Slam titles.
"In the grand scheme of things Novak winning four in a row again, it would be the most impressive thing we have ever seen," Wilander said.
The greatest of all time debate usually splits fans into the Federer and Nadal camps and Djokovic earns less adulation than those two.
"If Novak wins the French, suddenly then he has to be compared to the greatest players of all time," Wilander said. "He will have 16 (slams) if he wins the French. Okay Roger will still have 20 but it would be comparable because he would have won the Nole Slam twice, I mean that's unbelievable.
"To me that's incredible, Novak winning here is a bigger deal than Rafa winning 12 (French Opens). But then if Rafa wins, he's on 18 majors so it's getting crowded at the top."
Wilander said the French Open was 'monumental' in terms of the longevity of Nadal's career, saying a failure to retain his crown could have knock-on effects for the Spaniard.
"I think the bigger picture for me is more long term," Wilander said.
"If Rafa doesn't win the French, I kind of see him having a hard time winning Wimbledon or the U.S. Open... then next year's French Open comes into doubt.
"If Novak wins I mean the door will be wide open to reach 20 Grand Slams. Then if he equals Roger's 20 he would be regarded as the greatest player of all time."
That said, Wilander says this year's men's tournament is more open than usual with a host of young players such as Greek Stefanos Tsitsipas, Austrian Dominic Thiem, Russians Karen Khachanov and Daniil Medvedev and Chilean Cristian Garin equipped to cause trouble.
"So many guys hit the ball so hard today," Wilander said. "I'm not saying they will necessarily beat them but the worry for Novak or Rafa is how many matches will they be pushed to over the four hour mark in the first four rounds?
"Rafa, Roger or Novak against (Grigor) Dimitrov or (Kei) Nishikori, they have great records against them, but if Rafa played Tsitsipas he would be nervous from the first point. The young guys have less respect for reputations."