Roger Federer returns to John Millman during the fourth round...

Roger Federer returns to John Millman during the fourth round of the U.S. Open at the USTA Billie Jean King National Tennis Center on Monday. Credit: Kathleen Malone-Van Dyke

In tennis, people retire, sometimes more than once. It’s the verb the sport uses to describe a player quitting mid-match, usually because of injury or illness. It has nothing to do with hanging up the sneakers and going into another line of work.

Roger Federer has never retired. In 1,424 professional matches, he never has pulled out before the end. But that’s not the retirement people have been asking him about for, he said, “nine years.” Especially after such developments as Federer’s fairly astonishing upset loss to 29-year-old Australian John Millman, who entered Monday night’s U.S. Open fourth-round match with a career losing record of 46-58.

Federer struggled mightily with his serve throughout the 3-6, 7-5, 7-6, (7), 7-6 (3) shocker, his first loss in 41 Open matches against a player ranked outside the top 50. (Millman is 55th.)

So here is Federer at 37, the oldest man to have entered this year’s U.S. Open singles draw, and virtually without any unrealized goals in the game. He has won a record 20 major titles, 98 tour events in all. He has earned $117,507,812 in prize money.

A week ago, Federer caused a stir after commencing his 18th Flushing Meadows appearance with an 18th consecutive first-round victory, telling the Arthur Ashe Stadium crowd in a post-match interview that he was “happy I never stumbled at the first hurdle. It’s almost time to retire, but not yet.”

He immediately had to clarify that as “a total joke. I said maybe I could retire now, because I protected my 18 first-round wins here. That’s what I meant.”

There was a tennis website that, as an April Fool’s joke earlier this year, “announced” Federer’s tennis retirement. That, amid his repeated insistence that he has “no plans to retire . . .Don’t even write that word.”

To hear the questions about leaving the sport makes him more tired than playing. “I don’t know what to tell you,” he said. “In the beginning, you’re like, 'What? It can’t be true.’ Eventually, OK, fine, I get it. They’re allowed to ask it.

“Then you get to the point where everybody has to ask it because it could be that I would, in that very moment, reveal that this might be it. Then the journalist has to do the job and ask me that question. Almost every interview I do, they have to ask me the question, so . . .

“Sometimes you wonder why they ask you again because, do they not hear what I said yesterday? Do they not listen to what I said two months ago?”

What he keeps saying is that he is not retiring, that he enjoys the matches, the training, the travel — everything about his lifestyle. Furthermore, he’s still pretty good at his job, with a 36-5 match record and three more tournament titles in 2018 — including this year’s Australian Open — and the No. 2 ranking in the world.

As for Monday night, he admitted not handling the heat as well as Millman. “No shame there,” he said. “So, you know, move on and take a rest . . . and hopefully finish the year strong.”

And retire the talk about retirement.

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