Tiafoe, whose parents emigrated from the war-torn country before he was born, is the youngest American man to reach a U.S. Open quarterfinal in 16 years, and he has enough talent for two nations.In the stadiums and sports clubs of Freetown, Sierra Leone, soccer is the favorite topic. But on Tuesday, several hours after Frances Tiafoe, a son of two Sierra Leonean émigrés, beat Rafael Nadal to reach the quarterfinals of the U.S. Open, tennis has nudged itself into the conversation.“Oh, yeah, there is a lot of talk about Tiafoe right now,” Abdulai Kamara, a sports blogger and the owner of the Hereford Sierra Leone Football Academy, said in a telephone interview from Freetown. “We don’t really follow tennis closely here, but now there is some interest. Some people are curious about Frances, and they want to know more.”While the tennis community in the United States is excited that Tiafoe, who was born in Hyattsville, Md., has become the youngest American man to reach the quarterfinals of the U.S. Open in 16 years, some in Sierra Leone are proudly claiming the young tennis star as their own, too.The gregarious and talented Tiafoe, 24, has enough magnetism and dynamic tennis skills for two nations.The Sierraloaded publication referred to “Sierra Leone’s Tiafoe,” in a flash update on the historic win, and Kei Kamara, a soccer star from Sierra Leone playing for Montreal in Major League Soccer, wrote on Twitter, “One of us,” after Tiafoe’s win, calling it a “massive achievement.”Tiafoe’s uplifting story began when his parents — who had not yet met — left Sierra Leone for the United States in the 1990s to escape a civil war. They each moved to the United States and, after they met, settled down in Maryland and had twin boys, Franklin and Frances.The boys’ father, Constant Tiafoe, found work on the construction site for the Junior Tennis Champions Center in College Park, Md. Constant Tiafoe was so industrious, he was offered the job of the maintenance director of the facility. He was given an office, where sometimes the twins slept, the better to, as they grew big enough to hold rackets, spend time on the courts.They both played, but Frances displayed a unique passion, watching the lessons given to the older boys at the center and mimicking their every move, then hitting balls off walls and serving to ghosts on outer courts until dark.Tiafoe combines speed, power and court savvy.Gabriela Bhaskar for The New York Times“All the stories are true,” said Mark Ein, an entrepreneur and chairman of the Citi Open in Washington, D.C., one of the premier events on the tennis calendar. “Frances was obsessed with tennis.”Ein has known the Tiafoes since the boys were five and has become a friend, adviser and mentor. His own mentor was Ken Brody, an investment banker and tennis enthusiast who built the Junior Tennis Champions Center to enact a vision that Tiafoe might one day fulfill.“Ken used to say, ‘If the Czech Republic can develop champions in a country that size, then we can do it here in D.C.,’” Ein said.It was not long before Frances began to display a unique athletic agility — speed, power and court savvy — combined with a nearly unquenchable thirst for the game. He was paired with Misha Kouznetsov, a junior coach from Russia who pushed and pulled Frances through the early stages of his tennis development, which at times were remarkable.At first, the Tiafoes saw tennis as a vehicle for the boys to secure a university education, which only seemed attainable with a scholarship. Constant left his job at the training center to start his own business, but he ended up working at a carwash while the boys’ mother, Alphina, worked as a nurse. Money was scarce.“It wasn’t anything supposed to be like this,” Tiafoe said Monday after defeating Nadal. “Once we got in the game of tennis, it was like my dad was like, ‘It would be awesome if you guys can use this as a full scholarship to school.’ I mean, we couldn’t afford a university. So, use the game of tennis.”But Tiafoe shone so brilliantly at such an early age, that college was relegated to an afterthought as a lucrative professional career burst into view. When he was 14, in 2012, Frances won the prestigious Petits As tournament in France, around the same time that sports publications got wind of his humble and fortuitous upbringing at the J.T.C.C. The following year, Tiafoe won the Orange Bowl, a top tournament near Miami for the world’s best juniors. He was on his way, it felt.American tennis coaches, administrators, agents and the most knowledgeable fans began to see that Tiafoe might be the next great American player, which for so long had been a searing void in the game.But the development of professional players in today’s game often comes slowly, and Tiafoe has, at times, struggled. He turned professional in 2015, and for the next four years he reached the third round of a major tournament only once, at Wimbledon in 2018.He ended last year ranked No. 38 and is currently No. 26. That will improve after his breakthrough performance in the U.S. Open, no matter what happens Wednesday against the No. 9 seed, Andrey Rublev.Now Tiafoe’s popularity is rising fast, not only among Sierra Leonean soccer stars, but also from basketball megastars, including LeBron James, who congratulated Tiafoe on Twitter.“I mean, that’s my guy,” Tiafoe said of James, one of his sports idols. “To see him post that, I was like, ‘Do I retweet it as soon as he sent it? I was like, ‘You know what? I’m going to be cool and act like I didn’t see it and then retweet it three hours later.’”Tiafoe’s career has been defined by high expectations, plateaus, self-analysis and improvement.“There were such huge expectations for him at such an early age,” Ein said. “He achieved so many firsts, and he was considered the future, the hope of American tennis. That’s a lot for a teenager, and he handled it really well. He knows success is not always a straight line, but he also knows that if you are always headed towards true north, you can achieve your goals.”Ein and Tiafoe regularly swat an adage back and forth: that everyone wants to be a star like Beyoncé, but no one wants to put in the work to get there.During one of his plateaus, after the 2018 season, Tiafoe began to hear from people around him that he needed to train more, eat better, study film and improve his preparation — anything that might push him into the top 5 in the world.During the winter, over lunch in Georgetown, Tiafoe explained to Ein what he had been hearing and revealed his response to the well-intentioned pressure.“He told them, ‘Don’t worry,’” Ein recalled, “‘I got this.’ A few days later, he was on his way to Australia, where he reaches the quarterfinals of a Slam for the first time. That’s the Frances Tiafoe story.”Many people in the tennis world also know the story of Tiafoe’s early life in Maryland. But much of his tennis story is still heading north. Some of it is being written at the U.S. Open, and some of it is being written in Sierra Leone, where the legend of Frances Tiafoe is just taking hold. More