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Doha - World number one Novak Djokovic was buried by 21 aces as big-serving Croatian Ivo Karlovic on Thursday clinched a 6-7 (2/7), 7-6 (8/6), 6-4 victory to reach the Qatar Open semi-finals.
Top seed Djokovic joined second seeded Rafael Nadal on the sidelines after the Spanish star lost in the first round.
Karlovic, the 35-year-old world No 27, claimed his second career win over the world number one having also triumphed at the Madrid Masters in 2008.
He will face Spanish fourth seed David Ferrer for a place in the final.
In Brisbane, Swiss star Roger Federer won his 997th match on the ATP Tour on Thursday, but not before surviving an almighty scare from Australian wildcard John Millman.
Playing his first match of the year after receiving a first round bye, world number two Federer had to come from a set and a break down to overhaul Millman 4-6, 6-4, 6-3 in just over two hours.
Federer was out of sorts throughout the match against a player ranked 151 places below him, making 38 unforced errors - most of them in the opening set-and-a-half.
Millman, on the other hand, played some brilliant tennis, spurred on by the emotion of playing in front of family and friends on his home court.
Federer now plays another Australian wildcard, James Duckworth, in the quarter-finals following his 4-6, 7-6 (7/5), 6-3 win over Finland's Jarkko Nieminen.
Earlier, Canada's Milos Raonic fired off 17 aces in his 6-3, 6-4 win over Mikhail Kukushkin of Kazakhstan.
He next takes on fellow big server Sam Groth in the quarter-finals after the Australian won 6-4, 6-7 (2/7), 7-6 (7/3) over Polish qualifier Lukasz Kubot.
