World number one Novak Djokovic in action against Japan's Kei Nishikori.

Story highlights

Djokovic stunned in US Open

Lost to Japan's Kei Nishikori in four sets

First time Djokovic has lost to a young player in a grand slam

First Japanese player ever in a grand slam final

CNN  — 

World number one Novak Djokovic has sensationally been knocked out of the US Open.

The 2011 champion was beaten in the semi final in four sets by Japan’s Kei Nishikori 6-4, 1-6, 7-6 (7-4), 6-3 in what must go down as one of the biggest shocks of the modern era.

In staggeringly humid conditions Nishikori, who has been coached by former US player Michael Chang, burst out of the blocks and snatched the first set. Djokovic battled back to easily win the second. With the Serb ascendant, few gave Nishikori a chance against a player in his pomp who is considered one of the greatest of all time.

But Djokovic was clearly struggling with the conditions and gave up a succession of unforced errors and a string of uncharacteristic double faults.

Humid conditions

The match changed in the third set when it became clear that Nishikori was coping better with the heat, despite coming through two previous five set matches. The Japanese player won a third set tie break 7-4 before breaking Djokovic’s serve in the first game of the fourth.

A tiring Djokovic could do nothing to stop Nishikori, who powered on and became the first Japanese player, as well as the first Asian male player, to ever reach a grand slam final.

“I don’t know whats going on, I was a little tired,” an ecstatic and emotional Nishikori said on court shortly after his stunning victory.

“It’s my first semi final in a grand slam. It is an amazing feeling playing a number one player. So happy. It was really tough conditions today. But I love to play long matches! I hope I can recover well for the final.”

Although no one gave Nishikori a hope before the match, there were signs that Japan’s number one could spring a surprise after recently beating Roger Federer and narrowly losing to Rafael Nadal.

Equally as significant has been his teaming up with Chang.

“He’s been helping me a lot,” Nishikori said when asked about Chang’s influence on his game. “We have been working super well.”

A dejected Djokovic refused to blame the conditions for his defeat.

“It was the same for both players,” he said. “I congratulate Nishikori. He was the better player today … my game today was not even close to what I wanted it to be. A lot of unforced errors. I wasn’t myself.”

Ghosts of ‘33

Nishikori was the first Japanese player to reach a major semi final for 81 years. The last player to reach that level was Jiro Satoh, who reached five major semifinals, including Wimbledon in 1933.

But later that year Satoh committed suicide after jumping off the ship that was taking him and his teammates to England for a Davis Cup tie. Nishikori’s victory saw him surpass Satoh’s long running record.

“I hope it’s big news in Japan,” he said.

“I feel the support from Japan. It is 4am in the morning but I hope a lot of people are watching.”

Nishikori will play Marin Cilic in the final after the Croatian blew Roger Federer away in straight sets 6-3, 6-3, 6-4.

The day’s second semi final was delayed by rain, but when it restarted Federer must have wished for the heavens to open once again. Cilic attacked from the opening game, using his booming serve to devastating effect. Federer had no answers.

“It was an amazing day for me, to be able to play like this, it was the best performance ever in my career,” Cilic said on court after the game.

It will be a first grand slam final for both Cilic and Nishikori.

“I think it will be a sensational day for both of us,” Cilic said when asked about his Japanese opponent. “I’m just going to enjoy it, be happy and try to win.”

The 2014 US Open final will the first since the Australian Open in 2005 to not feature one of the big four of Djokovic, Federer, Nadal or Murray.