Doha: World number one Novak Djokovic was buried by 21 aces as big-serving Croatian Ivo Karlovic clinched a 6-7 (2/7), 7-6 (8/6), 6-4 victory to reach the Qatar Open semi-finals on Thursday.
Top seed Djokovic appeared affected by a steady breeze in the Qatari capital, which did not prevent Karlovic, the six-foot 11-inch, 35-year-old from taking his aces total to 67 in three matches.
Djokovic was nevertheless three times within two points of winning the match in the second set tie-breaker, before dropping serve for 3-4 in the final set as a visibly encouraged Karlovic came up with some fine forehand winners.
The top seeded Serb became sufficiently exasperated to fling down his racquet in the second set and then to sling it along the floor in the third.
He never looked likely to make a break back, eventually settling instead for congratulating Karlovic who claimed a second win over the world number onwe to add to his 2008 Madrid Masters victory.
"I was feeling good even though it was windy," said Karlovic. "I know he wasn't able to show his full range (of shots) because of the wind.
"I was relaxed and didn't feel I had to do anything extraordinary. I just had to focus on my game. So I guess I was luckier than him. But I am very happy that I won."
The result was even more surprising than the first round defeat of the titleholder Rafael Nadal, whose fitness problems had been well documented, and who was a long way from his best against German qualifier Michael Berrer.
True, Djokovic had been suffering from a fever prior to the tournament and had considered pulling out, but by the time he had dismissed Dusan Lajovic and Sergiy Stakhovsky for the loss of only six games in four sets he seemed to have recovered well.
Djokovic also started quite well against Karlovic, saving a break point with a fine first serve in the opening game.
Although he found it hard to make any headway against the steep and well varied Karlovic delivery, he served well enough himself and then lifted his level just at the right moments in the first tie-breaker.
But an inability to capitalise when he twice had Karlovic at 30-30 on his serve early in the second set seemed to frustrate Djokovic.
As this set wore on Karlovic began to sense that he might make major headway and the body language of both men changed notably.
At 3-3 in the decider Djokovic saved a break point with a serve, volley and smash combination, but slipped to break point down again by mistiming an inside-out forehand drive into the net.
He again made a good attempt to prevent a service break, landing a good serve and making a good volley from a decent forecourt position -- only for Karlovic to launch himself sideways and pull off his best shot of the match, a spectacular running forehand pass down the line.
Once again Djokovic held Karlovic to 30-30 on his penultimate service game, and again could not progress further.
Two games later when Karlovic was required to close out the win at 5-4 he completed it with a flourish, to love.
Djokovic trotted off to play a doubles match against Nadal, while Karlovic was able to contemplate that by having extended his total of aces in this match by another 21 to a career total of 9,062, he may well be able to overtake Andy Roddick's 9,074 this week.
He next faces David Ferrer, the fourth-seeded Spaniard, who reached the semi-finals with a 6-2, 6-2 win over Dustin Brown, a German who finished in the top 100 for the first time last year.