As the 10th day of play in New York moved deeper into the remote hours of the new morning, every passing game imbued Carlos Alcaraz with greater despair. From his focused start, the Spaniard’s intensity had flatlined and he could barely put a ball in court. He lost nine consecutive games against Ben Shelton and seemed to have nothing left.

Instead, the defending champion improbably dragged himself back into a contest that soon developed into one of the most remarkable matches of the year. The latest attempt by the second seed at orchestrating a monumental comeback was denied by a brave, defiant Shelton, the eighth seed, who refused to be shaken by his legendary rival or the looming prospect of securing the greatest win of career.

After 4hr 28min and at 3.33am, with the sun not long from rising over Flushing Meadows but with a half-full Arthur Ashe Stadium still hollering in unison until the end, Shelton ended Alcaraz’s reign with a 6-7 (5), 6-1, 6-3, 1-6, 7-6 (7) victory to clinch his biggest win yet and reach the semi-finals of the US Open.

In the aftermath of his dominant fourth-round victory against Tommy Paul, the expectations surrounding Alcaraz had risen exponentially as the seven-time grand slam winner attempted to defend his crown. His level in the first three sets of the match, however, more faithfully reflected the fact that this was his first tournament back from a four-and-a-half-month layoff.

This was a massive opportunity for Shelton and, under such unique circumstances, he showed that he has the inner belief and resilience to rise to these occasions. He managed this match spectacularly, pairing his typically devastating serving, variation and athleticism with solid returning and steadfast consistency across five sets.

Most important, he held his nerve until the end, even after squandering opportunities deep in the final set. “Carlos is one of the greatest champions in our sport already at 23 years old,” he said. “It’s always fun being on the court against him. It’s ridiculous some of the stuff he comes up with sometimes. The most enjoyable match that I’ve had in my career, for sure.”

Alcaraz left everything on the court, his lack of physical preparation also reflected in periods of fatigue and even vomiting into his towel on the court towards the end of the fourth set. Afterwards, he refused to leave the tournament downbeat after being part of such an immense battle against one of the best players in the world so early in his comeback from a serious injury. “As I said before the tournament began, my expectation was to go there, compete, play in these kind of matches for me being healthy,” he said.

“It was close. It was close. So I’m just not going to be disappointed about not getting the win at the end. You know, I’m just happy. I’m just proud about myself, about how I fought. After the third set, physically I was really tired, but you know I found a way to push myself up and physically giving extra.”

As a result of Alcaraz’s defeat, a new US Open champion will be crowned: 23 years after Andy Roddick’s triumph here, the last time an American man tasted victory at any grand slam tournament, Shelton will face his compatriot and friend Frances Tiafoe. “I was playing against one of the best – he is a beast,” Alcaraz said. “Shelton is an unbelievable player, powerful. He just managed to play really, really well in every situation, so credit to him. I leave the court happy. I leave the court with a smile, healthy, and this is what I needed.”

There are times when the tennis authorities make self-sabotaging decisions regarding scheduling, but sometimes it is just impossible to contain or plan for the greatness of this sport. This is, without doubt, one of the most incredible days of tennis in years. All four quarter-finals on Tuesday extended to deciding sets with Aryna Sabalenka, Tiafoe and Jessica Pegula each dragging themselves through spectacular comeback victories against Linda Noskova, Alex Michelsen and Emma Navarro respectively.

Alcaraz and Shelton did not start until 11.04pm, but over their subsequent four and a half hours on the court that was soundtracked by a delirious, raucous crowd until the very end, their battle provided the perfect climax to 16 hours of greatness, a night and morning that the thousands of roaring fans still present until the very end will never forget.

“It was just enjoyable to be a part of that match,” Shelton said. “Obviously the level of tennis, how long the match was going, the fight that it was, how even of a match it was back and forth throughout, I think that’s something we can appreciate. Win or lose, we would have a smile on our face.”