Twenty-three seconds. That is how long Frances Tiafoe held a sobbing Alex Michelsen in his arms just beyond the tramlines of Arthur Ashe Stadium on Tuesday, the winner consoling the loser after one of the most dramatic quarter-finals in recent US Open memory. Tiafoe had beaten his younger American compatriot 5–7, 3–6, 7–5, 6–3, 7–6(6) in four hours and thirty-plus minutes of relentless, lung-burning tennis to reach the last four at Flushing Meadows for the third time in five years. For the majority of the match, it was Michelsen who looked destined for glory.

The 22-year-old from Laguna Hills, California — unseeded and largely unheralded outside tennis circles — had surged two sets clear and was serving for the match in the third, with Tiafoe just two points from an early flight home. The mood inside a surprisingly half-empty Ashe Stadium was oddly flat, many fans still drained from Aryna Sabalenka's gruelling three-set opener earlier in the day. None of that helped the 11th seed, who had thrived all tournament in the louder, tighter atmosphere of neighbouring Louis Armstrong Stadium, where he has never lost in ten career appearances. Then something shifted.

Tiafoe, 28, began playing with a ferocity that had been missing for two full sets. He broke back, held his nerve through a tense fifth-set tiebreak, and ultimately proved why experience at a grand slam can be worth more than a two-set lead. "It was definitely a Braveheart-type win," Tiafoe said afterwards, placing the result among the greatest of his career.