Rafael Nadal's Australian Open hopes were dashed in cruel fashion as he retired through injury in the fifth set of his quarter-final against Marin Cilic.
Former US Open champion Cilic produced a hugely impressive display on Rod Laver Arena, his stinging, flat forehands a particularly potent weapon throughout a contest that was brought to a premature end after three hours and 47 minutes.
However, the Croatian was significantly aided by a clear deterioration in the fitness of Nadal, whose movement was compromised after he called for a medical timeout in the fourth set.
Although Nadal initially continued after receiving prolonged treatment on his upper right leg, he was ultimately unable to compete and retired when trailing 3-6 6-3 6-7 (5-7) 6-2 2-0.
Cilic will now face surprise package Kyle Edmund in the last four, with hopes of a rematch of last year's final between Nadal and Roger Federer having been sensationally ended.
The seriousness of Nadal's injury remains to be seen, but the top seed cut a forlorn figure as he exited the court to sympathetic applause, a day on from an ailing Novak Djokovic suffering defeat to Hyeon Chung.
Nadal failed to initially capitalise when a succession of Cilic errors provided him with five chances to break in the sixth game, but the world number one soon seized control before sealing the opening set with a forehand winner.
Cilic then fell behind early in set two, double faulting on break point after receiving a time violation, but a swift turnaround followed with the Croatian seemingly fired up by the umpire's intervention.
The aggrieved sixth seed duly reeled off four games in a row to level the match, enjoying particular success against Nadal's second serve as he adopted a more aggressive approach.
Amid rising tension, both men were showing emotion on an increasingly regular basis and a reflex volley from Nadal was followed by a trademark fist pump as he stopped the rot in the first game of the third set with a crucial hold.
After saving three break points and spurning a solitary opportunity of his own when leading 5-4, there was an even bigger reaction when the Spaniard eventually regained the advantage at the end of an absorbing tie-break.
Nadal let out a huge roar to celebrate putting away a smash on set point, but Cilic came storming back once again to break for a 3-1 lead in the fourth.
Out of the blue, Nadal then called for a medical timeout at the next changeover and received prolonged treatment.
His movement was significantly limited thereafter, even though he came from 0-40 down to hold in the next game, and Cilic suddenly looked a strong favourite as he broke again to force a decider.
That final set ultimately lasted just two games, Nadal bringing an end to proceedings after he had bravely saved five break points before finally falling 2-0 down.
Cilic now has a golden opportunity to reach his third grand slam final, while Nadal will await news on another painful injury setback.
Cilic  bt Nadal  3-6 6-3 6-7 (5-7) 6-2 2-0 Ret.
Cilic - 83/62
Nadal - 39/32
Cilic - 20/8
Nadal - 3/2
BREAK POINTS WON
Cilic - 5/19
Nadal - 2/10
FIRST SERVE PERCENTAGE
Cilic - 67
Nadal - 75
PERCENTAGE OF POINTS WON ON FIRST/SECOND SERVE
Cilic - 77/38
Nadal - 67/32
Cilic - 157
Nadal - 145
16. August 2018
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