Early mentors cheer Tiafoe's 'unbelievable' US Open run

Tiafoe executed the biggest upset of the tournament when he downed 22-times Grand Slam winner Rafa Nadal in the fourth round, raising hopes that he could help end a major title drought for the American men.

Spanish teenage sensation Carlos Alcaraz (19) stopped him in the semi-final Friday, but his performance still sent cheers of joy through his former academy in College Park, Maryland, where a crowd of roughly 50 gathered to watch him compete.

"Very proud of him, very proud of him. He’s unbelievable," Tiafoe's childhood coach at the Junior Tennis Champions Center (JTCC), Komi Oliver Akli, told Reuters.

"Hopefully he takes positives away and comes back and works harder."

Tiafoe's parents fled civil war in Sierra Leone in the 1990s and eventually settled in Maryland, where his father worked as an on-site caretaker at the JTCC. Frances and his twin brother regularly stayed the night, getting to hit balls on the courts.

"He always had a racquet in his hands. He was always hitting on the wall or he was always watching training," said Martin Blackman, the general manager for USTA player development, who was a coach at the JTCC from 2004 to 2008 when Tiafoe was there.

"Coaches would walk by and give him some tips, you know, but he absolutely loved it."

Tiafoe was offered a full scholarship to the 10-and-under programme when he was eight. Blackman said his extraordinary run some 14 years later in New York came as little surprise.

"It's a great breakthrough for him," he said. "He's put a lot of work in."

The training centre counts among its former pupils twice Grand Slam finalist Vera Zvonareva and Alison Riske-Amritraj, who reached the fourth round at Flushing Meadows this year.

At the JTCC on Friday, children hoping to follow in Tiafoe's footsteps stayed up past their bedtimes, cheering their throats raw whenever he scored a point.

"The whole nation is so proud of him, so let’s see what happens next year," said Akli.