(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.
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Djokovic stunned in US Open
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Lost to Japan's Kei Nishikori in four sets
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First time Djokovic has lost to a young player in a grand slam
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First Japanese player ever in a grand slam final
Novak Djokovic
Djokovic
Djokovic
Djokovic
But @placeholder was clearly struggling with the conditions and gave up a succession of unforced errors and a string of uncharacteristic double faults.
Novak Djokovic
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Djokovic
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The Japanese player won a third set tie break 7-4 before breaking @placeholder's serve in the first game of the fourth.
Kei Nishikori
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Nishikori
Kei Nishikori
"I don't know whats going on, I was a little tired," an ecstatic and emotional @placeholder said on court shortly after his stunning victory.
Michael Chang
Equally as significant has been his teaming up with @placeholder.
Kei Nishikori
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Kei Nishikori
"He's been helping me a lot," @placeholder said when asked about Chang's influence on his game.
Novak Djokovic
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A dejected @placeholder refused to blame the conditions for his defeat.
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Nishikori was the first @placeholder player to reach a major semi final for 81 years.