Stanislas Wawrinka sensationally ended Novak Djokovic's 25-match winning run at the Australian Open as he finally got the better of the defending champion.
As the clock registered four hours, Djokovic placed a volley wide on Wawrinka's first match point to give the Swiss a 2-6 6-4 6-2 3-6 9-7 quarter-final victory.
Djokovic was bidding to become the first man since Roy Emerson to win four straight Australian Open titles, and he had not lost a match since the US Open final in September.
Twelve months ago Djokovic won a fourth-round clash against Wawrinka 12-10 in the fifth set in Melbourne, while the outcome was the same when they met in the last four at the US Open.
Wawrinka said: "Last year it was really tough but this year I came back, it's a new year. I did not start well, I was not feeling great on the court. I tried everything. He's an amazing champion and he never gives up but I'm really, really, really happy."
Their clash in the fourth round last year was arguably the match of the season, so the Rod Laver Arena was primed for something special when the two men walked out under the lights.
It was something of an anticlimax, then, when Djokovic breezed through the first set.
But Wawrinka cut out the errors and found his form during the second set, ripping his one-handed backhand, and it paid dividends in the seventh game when he landed one on the line to break the Djokovic serve.
He nervelessly served it out, and in the third set the champion simply could not live with his opponent.
One thing that can be guaranteed from Djokovic, though, is a fight, and he let out an almighty roar when he broke the Wawrinka serve to lead 5-3 in the fourth set.
The Swiss had been 40-0 up but Djokovic somehow stretched to arc a return winner into the corner to set up break point and took it when Wawrinka blazed a forehand well out.
Wawrinka had two chances to break back but netted a forehand on the first and Djokovic served an ace on the second, while a second ace on set point drew another roar.
It seemed Djokovic had done the hard work when he broke again for 2-1 in the deciding set but he then threw in a poor game to hand the initiative straight back.
Djokovic had more chances in the fifth and seventh games but Wawrinka showed exceptional mental strength, and no little skill, to hold his opponent off.
There was more drama in the 11th game when, with Wawrinka leading 40-15, it began to spit with rain and there was a short delay.
It was no problem for the eighth seed, who finished off the game with an ace, and on they went.
Wawrinka was struggling a little with cramp but it was he who looked the more confident and eager to attack, and when Djokovic missed a backhand he had his first match point.
The Serbian looked set to save it as he positioned himself for a simple volley but as soon as he hit it the crowd knew Wawrinka had won the match.
In the last four he will face Tomas Berdych, who upset third seed David Ferrer 6-1 6-4 2-6 6-4 to reach the semi-finals in Melbourne for the first time.
Berdych joins Djokovic, Rafael Nadal, Roger Federer and Andy Murray in having made the last four at all of the grand slams.
The result is a big setback for Djokovic's hopes of reclaiming the world number one ranking from Nadal, while it is also an inauspicious start to his partnership with new coach Boris Becker.