At the junior tennis club in College Park that gave Tiafoe his start and where he still trains, coaches and aspiring players cheer him on, and never stop working.COLLEGE PARK, Md. — At the Junior Tennis Champions Center, Frances Tiafoe, the young American who has barged into the men’s singles semifinals at the U.S. Open by playing fearless, joyful tennis, simply goes by Frances.On Wednesday afternoon, as Tiafoe played his quarterfinal match against Andrey Rublev of Russia, the center’s students, coaches and staff members broke from their regular routines and threw a party for the facility’s most popular alumnus, and a rapidly rising tennis star they know as a friend.On an indoor clay court, sitting on folding chairs — but more often standing in excitement — more than 40 people watched Tiafoe’s match on a large inflatable screen. They hollered and held their breath as Tiafoe overpowered Rublev in straight sets to become the first American man to make the U.S. Open semifinals since 2006, when Andy Roddick lost to Roger Federer in the final.Amid the cheers for Tiafoe’s gargantuan serves and deft drop volleys, no one was far removed from the spirit of the center itself and the hard work it teaches, which got Tiafoe, 24, this far in the Grand Slam tournament. Between sets, at a coach’s urging, players raced to the courts for a few minutes of practice.‘He’s Always Happy on the Court’Komi Oliver Akli, 50, the center’s senior director of player development, trained with Tiafoe before the U.S. Open. “He was on the court every day, trying to put some work in, and he was working so hard,” Akli said.Erin Schaff/The New York TimesKomi Oliver Akli, a senior director of player development at the J.T.C.C. who immigrated to the United States from Togo in 1996, started working at the center in 2000, and met Tiafoe just a few years later when he was 5 years old.From a young age, Akli said he could tell Tiafoe had the skills to go far in professional tennis. “You don’t have to tell him too much stuff,” he said. “You just have to keep it simple for him. He just enjoys himself when he plays. He doesn’t care what it is.”There’s a room inside the facility, next to a fitness center and across the hall from the restrooms, with two desks, a cabinet and a refrigerator. Today, it serves as the offices of the center’s general manager and director of tennis. Until several years ago, the office still had two beds where Tiafoe, his twin brother Franklin, and their father Constant slept when Frances was a boy.Constant, who emigrated from Sierra Leone in the early 1990s, took a construction job on the crew that built the tennis facility, and he stayed on as a maintenance worker after it was completed. His starting salary was $21,000 a year, and the staff allowed him and his twin boys to sleep in the center a few nights a week and use the courts.When they weren’t at J.T.C.C., the twins stayed with their mother, Alphina, who also emigrated from Sierra Leone, but met Constant in the United States. Other relatives lived in a one-bedroom apartment in Hyattsville, just a few miles south of College Park.Since they met, Akli, now 50, said Frances Tiafoe hasn’t changed. “He never gets upset,” Akli said. “Never. He’s always happy on the court, enjoying himself on the court.”The J.T.C.C. is a nonprofit club that is focused on encouraging and supporting players from diverse backgrounds and concentrates on recruiting promising players from its own backyard.“It’s not a typical tennis club,” Joe Wilkerson, a vice president of the center, said. “We’re not a club. We’re not an academy. We’re a hybrid of all those things, plus what we do with community outreach in D.C.”It has 32 indoor and outdoor courts with hard, green clay and red clay surfaces, and offers programs and classes for various skill levels and ages, from beginner adults to children and teenagers aspiring to become the next Serena Williams, Roger Federer or Frances Tiafoe.After beating Rafael Nadal in the fourth round of the U.S. Open on Monday, Tiafoe said in a news conference that “it wasn’t supposed to be like this,” adding that he worked hard for his parents.“I just had a big passion for the game,” he said. “Not even mainly for me, but to do it for them.”Watching Tiafoe defeat Nadal was a special moment for Akli, especially because of the training they did together in College Park leading up to the tournament, Akli said.“He was on the court every day, trying to put some work in, and he was working so hard,” Akli said, adding that Tiafoe was especially focused on his fitness to go far in matches. “He was there with Rafa the whole time.”A U.S. Open Watch Party, With PracticeErin Schaff/The New York Times“He’s very much available to everybody when they’re here,” Joe Wilkerson, a vice president of the tennis center, said of Tiafoe.Erin Schaff/The New York TimesAfter Tiafoe took the first set against Rublev in a tiebreaker, Akli called out to the students, “Alright, guys. Let’s go.”The students jumped from their seats, grabbed their gear, and ran toward the facility’s indoor hard courts. Akli told the players to warm up and hit with a partner.“Then we can go back and watch another set,” he said.While the players hit forehands down the lines and cross-court backhands and forehands, Akli would occasionally check his phone, nestled in a basket of tennis balls, for the score of Tiafoe’s match.He was pleased to see Tiafoe tied at 4-4 in the second set, adding that Tiafoe had trained to go deep in sets if necessary. “I like the way he’s holding right now,” Akli said. “He knows his fitness.”Among the players who worked with Akli on Wednesday was Imani Jean, a 16-year-old who trains at the center full time. Imani starts her day at 7:30 a.m. for classes, tennis practice, fitness training, more tennis, and then more classes.Imani, who wants to play tennis at a Division I university before becoming a professional, said that she is inspired knowing she trains on the same courts where Tiafoe practiced and lived.“It definitely reassures me that I can get to that level,” she said.Even on days when he’s not playing in a tournament or training at the facility, Tiafoe’s presence is all around the grounds of the J.T.C.C., with framed pictures from when he was younger and enlarged news articles on the walls of the facility. Inside the lobby hangs a framed letter, with Tiafoe writing what he would have wanted to tell Arthur Ashe, the tennis star who died in 1993, after winning the ATP Ashe Humanitarian Award in 2020.“I know this is not just an award,” Tiafoe wrote. “It is a tremendous honor and a massive responsibility. I am not just that smiley kid on the rise anymore. I know I need to carry the torch and make a difference in the world.”Tiafoe went on to write that he wanted to be an example to younger children and “paint a picture for them that they did not know was possible.”“I want to help them make that a reality,” he wrote. “You showed so many of us the way, and now I want to pay it forward.”‘He Knows Them All By Name’Amari O’Brien, a 16-year-old who trains at the center full time, said she considers Tiafoe to be a friend.Erin Schaff/The New York TimesWilkerson said that when Tiafoe is there, he makes himself open and accessible to the young players.“He knows them all by name,” Wilkerson said. “He’s very much available to everybody when they’re here. It’s probably sometimes to his own fault.”Amari O’Brien, 16, who trains at the center full time, said she considers Tiafoe to be a friend.“It’s just it’s kind of bizarre to think that he trained here,” Amari said, adding that she hopes that she can one day be in the same position as Tiafoe.Amari came to practice at the J.T.C.C. for two weeks in 2019, and earned a scholarship to train full time. Her parents eventually moved to Maryland from Michigan to support her.Wilkerson said that scholarships at the center help make tennis accessible to more people.“That is our ultimate goal,” Wilkerson said. “If a kid shows the promise and the passion and the love and respect for the game, then we will make sure that we can fund them and get them through the program.”It’s not just children and teenagers who come to the center. Charles Abety, 50, who lives in nearby Greenbelt, Md., started taking tennis lessons at the J.T.C.C. about four months ago.“I wanted to have something that I could do that I love,” Abety said while watching Tiafoe’s match, adding that he’s “very much” inspired by Tiafoe.After more training in the afternoon, the players returned to the watch party to see Tiafoe in the third set against Rublev. When Tiafoe won the set and clinched the match, advancing to the semifinals with an ace, the players, coaches, staff members, and parents of players at the center jumped to their feet and clapped.“Let’s go, J.T.C.C.” Akli yelled.But the applause and cheers were brief. The players didn’t stick around for Tiafoe’s post-match remarks on the court. They ran to grab their gear again. It was time to train.Erin Schaff/The New York Times More