AILSA CHANG, HOST:

All right. The U.S. Open tennis championships are suddenly all about transition. Certainly, that was the case with last week's probable farewell by American star Serena Williams. But since then, huge upsets on the men's side are signaling a possible changing of the guard as well. None was bigger than yesterday's win by American player Frances Tiafoe over 22-time Grand Slam singles champion Rafael Nadal. NPR's Tom Goldman has been covering the tournament and joins us now. Hey, Tom.

TOM GOLDMAN, BYLINE: Hi there.

CHANG: Hey. OK. So how surprising was Tiafoe's win yesterday?

GOLDMAN: Very. The two were playing for a berth in the quarterfinals, and Nadal had made at least the quarterfinals in 16 straight Grand Slam tournaments...

CHANG: Wow.

GOLDMAN: ...Dating back to 2017. The two times he'd played Tiafoe in 2019, Nadal won without losing a set. And Nadal won the first two Grand Slam tournaments this year - could have won a third but had to pull out of Wimbledon with an injury. So, Ailsa, there were no obvious signs of his early demise in New York. He had been starting slowly. Two of his first three matches, he lost the first set before fighting back in true Nadal fashion. Most expected that would happen again versus Tiafoe. But Tiafoe had Nadal on his heels the whole match. He was quicker, his serve more powerful. Groundstrokes were lethal and had Nadal scrambling all over the court - so no comeback this time for Rafael.

CHANG: Sorry. So can we just step back for a moment? Can you tell us a little more about Tiafoe's backstory?

GOLDMAN: It's a great story. His parents are immigrants from Sierra Leone. As described in the ESPN website Andscape, Tiafoe was the poor kid who fell in love with a rich man's sport. He was the son of a tennis center custodian wearing hand-me-downs. Yesterday after his big win, he talked about how he was inspired by the Williams sisters and what it was like to have his parents at yesterday's match. Here he is.

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FRANCES TIAFOE: Watching young Serena and Venus play, following the Grand Slams at that time and - when I was super-young and - I was like, you know, how cool to be to play with them and to play, you know, unauthorized and stuff like that? And to see them experience me beat Rafael Nadal, you know, to beat, you know, those Mount Rushmore guys - yeah. I mean, they're going to remember today for the rest of their lives.

CHANG: (Laughter) I bet they will.

GOLDMAN: So is he.

CHANG: Beating those Mount Rushmore guys - well, Tom, I mean, we haven't seen much from American men in recent years when it comes to Grand Slam tournaments, right? Like, does Tiafoe's success mean there's a shift going on, a good one?

GOLDMAN: Well, his emergence is exciting. He's only 24. He's part of a collection of good young U.S. men players, but he's also the only one of them to make it as far as the fourth round. The last time an American man won his home tournament, the U.S. Open - that was Andy Roddick in 2003. Now there's hope Tiafoe can break that nearly 20-year drought. But with Nadal out and No. 1 seed Daniil Medvedev out, the men's side is wide open and very young. The old man of the quarterfinals is Nick Kyrgios of Australia. He's only 27.

CHANG: Wow. You say wide open and very young. I mean, that's a real change - right? - because the big three in the men's game - they're all now in their - what? - mid-30s, early 40s. And they basically have had a lock on the Grand Slams for so long, right?

GOLDMAN: Yeah, absolutely. Nadal, Roger Federer, Novak Djokovic - they've defined the men's game for a generation. This U.S. Open is the first time since 2003, again, where none of the big three nor Serena Williams has made it to the quarterfinals of a Grand Slam tournament. So, yeah, this tournament really seems to be a turning point, although on the men's side, the big three still are planning to play next year and maybe beyond. So the end isn't imminent, but it's coming.

CHANG: That is NPR sports correspondent Tom Goldman. Thank you, Tom.

GOLDMAN: You're welcome.

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