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On Wednesday, Hubert Hurkacz, a man who had won only four matches on grass before this fortnight, could well have made those fears a reality after he produced an inspired display to hand his childhood idol a 6-3 7-6(4) 6-0 mauling in the quarter-finals.
Federer, the winner of 20 Grand Slam titles, had been chasing Martina Navratilova's All England Club haul of nine singles titles.
Before Wednesday, the eight-times champion had contested 404 sets at Wimbledon since making his debut in 1999 and never before had he lost one 6-0 at the grasscourt major.
If the 407th set he contested at the All England Club does turn out to be his final hurrah, it will be a sad ending to the Wimbledon career of a man John McEnroe describes as a "tennis god" whose exquisite shots have wowed and thrilled fans for over two decades.
"I don't know if we will ever see the great man again here," former champion Boris Becker said, voicing the fears of many millions.
A despondent Federer could not rule it out either.
"I don't know. I really don't know," admitted the 39-year-old Swiss, who had been bidding to become the oldest man in the Open Era to reach the last four at Wimbledon.
"I'm not used to that kind of situation... especially not here."
It had been 18 months since Federer last played five matches at the same tournament as two surgeries on his right knee kept him out of the sport for more than a year after his semi-final loss at the 2020 Australian Open.
For him, the decisions he made with his 40th birthday looming in August - to go under the knife, or spend many hours in rehab, or pull out of last month's French Open after he had won his third-round match - were all because he wanted to hold up the pineapple-topped Challenge Cup for a record ninth time.
The fact that the dream ended in a 0-6 nightmare must hurt, and hurt bad.
"I feel horribly exhausted. I could go for a nap right now. That's how I feel," said Federer, who missed out on winning a record 21st Grand Slam title in the same arena two years ago after squandering two match points in the final against Novak Djokovic.
"You put everything on the line, and when it's all over you could just go sleep because you're so exhausted mentally. The last 18 months have been long and hard."
When things go wrong in the manner they did on Wednesday, the Swiss great will leave Wimbledon with more questions than answers about his future.
Facing a Polish opponent who had never previously strung together more than two wins at a Grand Slam, not many had thought Federer's pursuit of a 14th Wimbledon semi-final, and 47th across all four majors, would come unstuck in the way that it did.
When the Swiss survived three break points to steam ahead 3-0 and 4-1 in the second set, the fans stopped biting their nails and settled back into their seats confident it would only be a matter of time before Federer levelled at one-set-all with Hurkacz.
But the dazzling Federer winners, which have flowed off his racket like liquid gold over the years, were in short supply against the Pole who was just two when the Swiss made his Wimbledon debut.
Instead there was a steady flow of shanked backhands, netted volleys and wayward forehands -- not the kind of shots that had earned him 369 match wins at the majors.
When he stumbled and missed making contact with the ball in what should have been an easy smash -- the alarm bells started ringing louder and the chants of "Let's go Roger, let's go" also hit fever pitch.
However, all the cheers and standing ovations in the world could not save Federer on Wednesday as it seemed his 39-year-old body finally said enough is enough.
A Federer forehand into the tramlines handed Hurkacz the biggest win of his career.
"Clearly there's still a lot of things missing in my game that maybe 10, 15, 20 years ago were very simple and very normal for me to do. Nowadays they don't happen naturally anymore," Federer said.
"I have a lot of ideas on the court, but sometimes I can't do what I want to do."