Editor’s note: An original version of this story was published in January 2025.The Athletic has live coverage of the 2026 U.S. Open. For a few hours on a sparkling mid-December morning in Southern California, two guys who figure to play a major role in the future of American men’s tennis beat balls across the net of a neighborhood hard court.On the other side of a chain-link fence, a women’s pickleball foursome click-clacked through a couple of sets, seemingly clueless about the identity of the two young men readying themselves for the start of the 2026 season. The yelps and chatter of a nursery school recess clattered down from a small hill overlooking the scene.Across the globe, other members of the ATP Tour top 40 were likely going through their paces at exclusive clubs or those vaunted academies built on Rafael Nadal’s or Patrick Mouratoglou’s name. Alex Michelsen and Learner Tien were fine to do their thing in Mission Viejo, just inland from Laguna Beach.“I hate myself!” Michelsen screamed after a soft approach gave Tien an easy passing shot.That brought out a little grin from the 20-year-old, who already has one of the great tennis poker faces. There were a few more grins that morning, including when Michelsen missed an easy volley.“I should be shot!” he yelled.Before long, they were playing a 10-point match tiebreak, with the rules according to the Next Gen ATP Finals, the tournament for the best players aged 20 and under, which Tien went on to win a week later. Michelsen aced Tien with a serve that ticked the top of the net before dribbling over. He apologized.“We can redo it if you’re really sorry,” Tien suggested.“I’m not that sorry,” Michelsen, 21 at the time, said. He won the tiebreak a few points later.Within a few minutes, they were sitting on the bench beside the court, with Michelsen seeking some relationship advice from his partner in a climb to the top of their country’s tennis mountain that started in the same Orange County hills. Sometimes they were on neighboring courts at the same tennis center. More often, they shared fitness sessions on the beach.Alex Michelsen is figuring out how to map the contours of his game to success on the ATP Tour. (Patrick Hamilton / AFP via Getty Images)Tennis moves fast. The current U.S. generation, led by Taylor Fritz, Frances Tiafoe and Tommy Paul, is suddenly a collection of players in their late 20s running up against time. All of them registered head-scratching losses during the season’s first week, but this U.S. Open has looked a little different.Ambivalence has laced through Tiafoe’s relationship with tennis, though he declared himself fit for purpose at the start of the year and is back in the quarterfinals of his favorite tournament after one of the most consistent seasons of his career.Paul was banged up for the final six months of the 2025 season. He has been mostly healthy this year but bumped into his ceiling again Sunday, losing to Carlos Alcaraz in straight sets in the fourth round.Fritz, who has largely stood apart from his compatriots in how he has maximized his talent — regularly playing on the biggest stages against the biggest stars — hit something more like a wall. He was upset in the third round Saturday by Francisco Cerúndolo, the No. 24 seed from Argentina, who came back from two sets and a break down.Ben Shelton, 23 and the senior in Tien and Michelsen’s cohort, is the top-ranked American man now. He and Michelsen charged into the U.S. Open quarterfinals Sunday, with wins full of flash and firepower. Tien, the No. 14 seed, has the chance to join them when he faces the unseeded, but richly experienced, Karen Khachanov in his fourth-round match Monday.Michelsen already has plenty of big wins, a huge serve and tons of upside, according to most high-quality tennis minds. At the 2025 Australian Open, Shelton, Tien and Michelsen were three of four American men to make the second week. Paul was the other.Seven Grand Slams later, Tiafoe has joined them in composing the tip of the spear to break the 23-year Grand Slam drought for the American men. Shelton figured to have the best shot after crushing Stefanos Tsitsipas, 6-2, 6-3, 6-4, Sunday night, but he faces a suddenly in-form Alcaraz in the quarterfinals next.“It’s going to be fireworks Tuesday night,” Shelton said on the court after his latest win.Michelsen has yet to lose a set in four matches. He barreled through Tomás Martín Etcheverry of Argentina on Sunday afternoon at Grandstand. He flipped the match over 4 points in the first-set tiebreak, saving a set point for Etcheverry on the Argentine’s serve by knifing a backhand volley winner. Two big serves later, he clinched the set by grinding out a 24-shot rally.The turnaround rocked Etcheverry.“He’s American, he’s playing here with the people — everyone supports him, of course — and he’s motivated,” Etcheverry said after the match. “He didn’t lose a set in the last four matches. He’s been unbelievable. I think he has good chances in the next round.”