Young players are stepping up as some older ones fade. Even Roger Federer, the event’s father, has retired.Coming into this year’s U.S. Open, Ben Shelton felt that he had something to prove. But it didn’t have anything to do with the final major championship of the year, where he reached the semifinals before falling to the eventual winner, Novak Djokovic.Instead, Shelton thought he had to justify his inclusion on the six-man Team World in the Laver Cup, an elite competition that begins Friday at Rogers Arena in Vancouver, British Columbia.“When the announcement first came out, I saw all these comments on Instagram, like, ‘Why did you take him? Why? Why this guy? There’s so many higher-ranked players,’” said Shelton, who entered the U.S. Open at No. 47 in the world but is now No. 19 because of his semifinal finish in New York. “I wanted to show people that maybe I deserved to be on the team.”The Laver Cup began in Prague in 2017 and trades continents each year between Europe and North America. Team Europe, captained by Bjorn Borg, who won 11 majors, features Andrey Rublev, Casper Ruud, Hubert Hurkacz, Gaël Monfils, Alejandro Davidovich Fokina and Arthur Fils. John McEnroe, who won seven major singles titles, is captain of Team World. His players are Shelton, Taylor Fritz, Frances Tiafoe, Tommy Paul, Felix Auger-Aliassime and Francisco Cerundolo.Last year’s event in London was noteworthy because it featured Roger Federer’s final match before retirement. His greatest rivals, Djokovic, Rafael Nadal and Andy Murray, all showed up to honor him. His last match, a doubles loss with his teammate Nadal to Tiafoe and Jack Sock, was a tearful tribute to the 20-time major champion.This year’s Laver Cup represents a generational shift in the sport. Federer has retired, and Nadal, 37, has not played an ATP match since the Australian Open in January because of injuries.Murray, at age 36, is not the player he was when he captured the U.S. Open in 2012, Wimbledon in 2013 and 2016, and became world No. 1 in 2016. And Djokovic, who won his 24th major at the U.S. Open less than two weeks ago and is the current No. 1, is focusing on winning another major.“The end of an era heralds the beginning of a new one,” said Rod Laver — the player for whom the competition is named — who was part of his own generation’s rivalries with Ken Rosewall, John Newcombe, Arthur Ashe and Jan Kodes, among others. “Today’s leading younger players are jockeying for pole position, and we’ll get to see them competing in a team setting in Vancouver, which weaves the eras together.”Bjorn Borg, left, is the captain of Team Europe, and John McEnroe leads Team World.Andrew Boyers/Action Images, via ReutersMcEnroe, who had his own spirited rivalries with Borg, Jimmy Connors and Ivan Lendl throughout the 1970s and ’80s, lamented that the Laver Cup had not generated the same appeal among the players as the Ryder Cup, the team event in golf.“The goal was to make it like golf’s Ryder Cup, where everyone was waiting until the last minute to see who was hottest, but everyone was available,” McEnroe said. “It doesn’t seem to be the case now. It’s tougher to get everyone committed.”Carlos Alcaraz, the reigning Wimbledon champ and world No. 2, has declined to play, as has the U.S. Open runner-up and the world No. 3, Daniil Medvedev. But six of the next 11 ranked players are competing this year, and three others, Alexander Zverev, Stefanos Tsitsipas and Alex de Minaur, have played in the past.This year, Team Europe will play without its powerful core of Federer, Nadal, Murray, Djokovic, Alcaraz and Medvedev. Winners in each of the first four years, the Europeans lost on the last day last year when Team World’s Auger-Aliassime beat Djokovic and Tiafoe outlasted Tsitsipas.Paul, who beat Alcaraz in a tournament in Canada this summer but then lost to Shelton at the U.S. Open, said he was keenly aware of the void left by the Big Four.“It’s definitely a big loss for tennis in general, not just Laver Cup,” he said. “It obviously gives us a pretty good opportunity.”Fritz, who last year won his only Laver Cup singles match, acknowledged the generational shift.“I think times are definitely changing,” said Fritz, who is the top-ranked American at No. 8. “It’s going to be a really different Laver Cup this year with how Team Europe is made up.”Tiafoe, who lost in the U.S. Open quarterfinals to Shelton, agreed.“Yeah, it’s generational,” Tiafoe said during the Open. “I think the fans are going to appreciate the new faces. Tennis is at a great place; the level is getting better and better.”“When I was watching on TV, I was thinking, the way they are so excited, it’s not real,” Andrey Rublev said. “But when you get there, you want to win. You get with the team, you start to feel the support, and you don’t want to let them down.”Mike Stobe/Getty ImagesBefore he first played in 2021, Rublev was skeptical of the event, which awards no ATP ranking points.“When I was watching on TV, I was thinking, the way they are so excited, it’s not real,” he said. “But when you get there, you want to win. You get with the team, you start to feel the support, and you don’t want to let them down.”Fritz is also aware of the camaraderie of the team competition that is so rare in tennis. Last year, members of Team Europe watched a doubles practice session between Federer and Nadal and Murray and Djokovic. Both teams sat intently on the sidelines during each match, cheering and giving coaching advice.In tennis, when you win, Fritz said during the U.S. Open, “you don’t really have people to celebrate with and have fun with. Winning last year, I felt like that was one of the top moments of my tennis career because we were able to celebrate with a group of my close friends.”Seismic movements in tennis are nothing new. After Laver and his rivals, and Borg-McEnroe-Connors-Lendl, came Pete Sampras, Andre Agassi, Jim Courier and Michael Chang. Each time an era ends, there are those who feel that there can never be one as great.Then came Federer, Nadal, Djokovic and Murray. And now Alcaraz has emerged to challenge Djokovic, as have other talented young players.Shelton, who turns 21 next month, is one of them. A former player at the University of Florida, he helped the Gators to the 2021 N.C.A.A. team championship. He then won the N.C.A.A. singles title the next year before leaving school and turning pro last year.At the Open this year, Shelton became the youngest American man to reach the semifinals since Chang did in 1992. For Shelton, the Laver Cup has a special attraction.“I’m pretty pumped to be in the team atmosphere,” he said at the U.S. Open. “First team competition I’ve been part of since I left college. I’m going to be just as amped and emotional in Vancouver as I was here.” More