Andy Murray was knocked out of the US Open at the hands of Kei Nishikori in an enthralling quarter-final match at Flushing Meadows on Wednesday.
The Japanese, who lost out to Murray in the Olympic semi-finals last month, recovered from a worrying start to come away with a 1-6 6-4 4-6 6-1 7-5 victory.
After struggling to cope with Murray's strong returning in the opening set, Nishikori battled back after a rain delay to stun the world number two.
The result marks just a second victory for the 2014 finalist over Murray in nine attempts.
A long backhand from Nishikori earned Murray his first break to go 3-1 up, and the Briton's vicious return of serve saw him power to a swift first-set victory.
Murray's dominance of the opening set faded in the second and, although he made the first break, Nishikori immediately pegged him back in a pattern that would later become a recurring theme.
After a pause for the roof to be closed, Nishikori levelled matters as Murray found the net following a long rally.
Nishikori appeared to have the crowd on his side against a visibly frustrated Murray.
The Japanese twice came up with an immediate response to Murray breaks during a tight third set, but the Olympic champion made a third gain stick and held serve to go back in front.
Having started with a dominant 6-1 victory, Murray's match was flipped on its head when Nishikori claimed the fourth by the same scoreline as part of a seven-game winning run.
Murray finally stemmed the tide by holding serve to pull back to 2-1 in the decider and he converted a second break point to pull level.
It proved to be brief respite for Murray, though, as Nishikori fired a winner down the left to regain the advantage, but a match of twists and turns had another twist - and turn - to come.
Murray's break to level at 4-4 had the feel of a moment that could shift the momentum in his favour, yet Nishikori - chasing just a second grand slam semi-final appearance - would come again.
A double fault from Murray handed Nishikori a break point that was duly converted to the fury of the Wimbledon champion, and the 26-year-old held serve to wrap up a memorable win.
Nishikori will face Juan Martin del Potro or Stan Wawrinka for a place in the final.
Nishikori  bt Murray  1-6 6-4 4-6 6-1 7-5
Nishikori - 48/60
Murray - 29/46
Nishikori - 1
Murray - 8
BREAK POINTS WON
Nishikori - 9/13
Murray - 8/15
FIRST SERVE PERCENTAGE
Nishikori - 60
Murray - 55
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Nishikori - 72/43
Murray - 69/39
Nishikori - 142
Murray - 130