“It could be argued that Francis is the luckiest kid in the world,” Ray Benton, the tennis center’s chief executive, said. “It was pure serendipity. He didn’t pick tennis; tennis picked him.”

When the French Open begins May 27, analysts and fans will lament the state of men’s tennis in the United States. John Isner is the top-ranked American at No. 10, and he is hardly considered a formidable threat to win a Grand Slam tournament. The last American man to win a major was Andy Roddick, at the 2003 United States Open. If Francis continues his ascent, he could be the country’s next, best hope in the sport — a notion that would have been inconceivable to his parents when they immigrated from Sierra Leone in the early 1990s.

Tiafoe and his wife, Alphina, had twin boys in 1998, and two years later he took a job on the construction crew that was building the tennis facility.

“I worked harder than everybody else as I was the only black guy on the crew,” he said.

When the club was completed, Tiafoe was hired to do maintenance. Responsible for opening and closing the center, and everything in between that did not directly involve tennis, he often slept only three hours a night. His starting salary was $21,000 a year. When the staff told him he could stay in the spare office, he made it a home for him and the boys, who stayed at least five days a week. The rest of the time the children stayed with Alphina, who lived with relatives in a one-bedroom apartment in nearby Hyattsville.