Kei Nishikori , 10th seed in the tournament, beat Novak Djokovic 6-4,1-6,7-6(7-4), 6-3 and will face Marin Cilic in the finals on Monday after the Croat humbled Roger Federer in straight sets.
The Japanese man responded well after dropping the second set to seal a glorious win.
“It’s just an amazing feeling, beating the number one player,” said Nishikori.
“I hope it’s big news in Japan. I feel the support from Japan. It’s 4 o’clock in the morning but I hope a lot of people are watching.”
Nishikori had to play 10 sets in more than eight hours in his two previous matches, but produced an awesome performance as temperatures hit 36 degrees.
“It was really tough conditions today, it felt a little bit heavy and humid,” he added. “I guess I like long matches.”
Few expected Nishikori to test Djokovic after having two gruelling wins over Milos Raonic and Stan Wawrinka in previous rounds.
The player had the better start, breaking the world number one twice to claim the first set. The Serb came back in the second set, blowing through his opponent in thirty minutes.
The third set was the game decider, Nishikori survived four break points and seven deuces to secure a pivotal set which brought the crowd to its feet.
Flashing backhand and forehand winners had Djokovic reeling as Nishikori broke for 5-3, but a nervous service game followed and he double-faulted when trying to close out the set.
Again, it appeared that Djokovic would finally assume control and power on to a fifth straight US final, but the top seed continued to struggle and played a poor tie-break.
A wayward forehand on set point was his sixth unforced error in 11 points and the prospect of a major shock became very real when he then dropped serve at the start of the fourth set.
Djokovic got frustrated and seemed to be out of ideas. Nishikori, on the other hand, had one more challenge in the final set. He played his way out of trouble from 0-40 to move 2-0 up, Djokovic couldn’t recover after that missed opportunity.
Another searing backhand return brought up two match points and Djokovic’s challenge ended with a tired forehand over the baseline.
“Other than that second set my game today was not even close to what I wanted it to be,” said Djokovic.
“A lot of unforced errors, a lot of short balls. I just wasn’t myself.”