Kei Nishikori was a hero in Japan long before he arrived in New York a fortnight ago but will have taken his star status to another level after he recorded a stunning victory over Novak Djokovic last night to reach the final of the US Open.

The 24-year-old produced the performance of his life to beat the world No 1 6-4, 1-6, 7-6, 6-3 to become the first Asian man to reach a Grand Slam singles final.

"It's 4am in Japan but I hope a lot of people are watching," said a jubilant Nishikori, who will take on the winner of last night's second semi-final between five-times champion Roger Federer and Croatia's Marin Cilic.

"I don't know what's going on. I was a little tight, in my first semi-final of a Grand Slam, but it's an amazing feeling, beating the No 1 player in the world and playing much better these last few matches."

Few people gave Nishikori much hope of beating Djokovic, who had looked so strong in overcoming Andy Murray in the quarter-finals and who looked full of confidence after winning Wimbledon. The Serb should also have been far fresher than Nishikori, who had to cope with back-to-back five-set, four-hour-plus matches to make it into the last four for the first time.

But on another brutally hot day at Flushing Meadows, Djokovic seemed to wilt and Nishikori was a deserving winner, clinching victory when Djokovic sent another forehand long. "I just wasn't myself," a dejected Djokovic said. "I think he just played better in these conditions than I did. Other than that second set, my game today was not even close to what I wanted it to be. A lot of unforced errors, a lot of short balls."

What makes Nishikori's achievement even more amazing is that he almost didn't play here after having a cyst removed from his right foot last month.

But right from the start of the match the Japanese looked the more comfortable, breaking in the third game. Djokovic broke right back but Nishikori broke to lead 4-3 and held the advantage to take the opening set.

Djokovic looked to have sorted himself out when he raced through the second set, hitting with more spin and taking Nishikori out of his comfort zone.

An epic third game of the third set, which lasted more than 10 minutes before Nishikori held, changed the momentum of the match into his favour again. When Nishikori broke to lead 5-3 in the third - and then double-faulted to be broken - it felt as if the world No 1 would slam the door shut.

But Djokovic played a poor tie-break to go two sets to one down. Nishikori broke in the first game of the fourth and showed no nerves as he broke again to clinch a huge victory.

Twelve months ago, Nishikori lost in the first round but his decision to hire former Grand Slam champion Michael Chang as his coach has proved to be something of a masterstroke. He has always been flashy but mentally and physically he is now a different animal. Whatever happens in tomorrow's final, Nishikori is guaranteed a huge reception next time he returns to Japan, as Djokovic generously agreed.

"This is definitely huge for Japan and this can definitely be a great encouragement for tennis in that country," he said. "Kei has been around for a few years and has had a lot of success but getting to a final of a Grand Slam is something different; it's another level."

Having played two five-setters and a mentally-taxing four-set battle against Djokovic, Nishikori will now rest and prepare himself for the biggest match of his career.

"Conditions were heavy and it was very humid," he said. "But I like to play long matches, I guess. Hopefully I can recover well for the final."