The tennis world won't see Roger Federer in action again this year, and by the time 2021 rolls around, the dominant player we've come to know and love may be lost forever.
That's the concern of two leading tennis experts, who believe the nature of Federer's injury, and the Swiss great's advancing years, spell trouble for his prospects of another incredible comeback.
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Federer already defied critics after coming back from a long injury lay-off to win the 2017 Australian Open against Rafael Nadal.
The Swiss ace followed up that against-the-odds triumph with another two grand slam singles titles for good measure - to extend his record haul.
However, there is a growing sense that Father Time will finally catch up to him this time, in the wake of his latest injury lay-off.
The tennis world was left shocked and saddened last week when Federer announced he had suffered a setback while working back to fitness in rehabilitation during the coronavirus pandemic.
Federer, 38, had been back in training after undergoing knee surgery after the 2020 Australian Open.
However, the latest injury setback will see him sit out the remainder of the Tour, if it resumes as planned in the wake of the coronavirus pandemic.
Already concerns have been raised about how a 39-year-old Federer will fare in 2021, with so little tournament tennis under his belt.
Renowned coach Brad Gilbert says while he is reluctant to "write him off", he thinks the odds of Federer being able to get back to his best are slim, considering it can often take much younger players up to six months to regain full competitiveness after a long injury lay-off.
“I’m not going to write him off, but this is concerning,” Gilbert told ESPN.
“Thirty-nine ain’t what it used to be, that’s for sure. But if tennis gets going again, he’ll probably be unseeded for the Australian Open in ’21 because he played so little early this year. And that could mean trouble.”
“We are in uncharted territory, the way guys are training and taking care of themselves.
“Sure, Ken Rosewall and Jimmy Connors [both played in majors after turning 39], but today’s game is more physical, and the players are tougher.
"When you take that much time, even at 25-26, it can take six months to get your mojo back.
Djokovic and Nadal tipped to break Federer’s record
Former Wimbledon winner Goran Ivanisevic shares similar concerns, insisting that Federer's injury puts Novak Djokovic in the box seat to overtake the Swiss maestro's record 20 grand slam singles titles.
“Unfortunately, I don’t think Federer will win any more Grand Slams, because he certainly won’t come back younger. But Federer should not be written off,” he told Nova TV
“It’s difficult for me to give an answer because in my opinion Novak is the best and he is the only one who can win a calendar Grand Slam.
“If he’s healthy, I think he’ll break that record [of 20 Grand Slams]. I think Nadal will break Federer’s record as well.
While Federer has announced he won’t be returning in 2020, it is unclear how much of the Tour he will miss.
Djokovic indicated that he would rather skip the US Open - if it goes ahead - and return to competition on clay ahead of the rejigged French Open schedule.
Nadal has also expressed concerns over travelling to the US under strict restrictions.
The ATP Tour has been suspended since 12 March due to the coronavirus pandemic, with Wimbledon cancelled for the first time since World War II.
The French Open was postponed in an attempt to play it at the end of the year, with officials yet to confirm whether it will go ahead in 2020.
The United States Tennis Association (USTA) is tipped to announce this week that the US Open will go ahead.
The New York grand slam is expected to run as originally scheduled from August 31 to September 13, albeit without spectators.