Evgeny Donskoy produced the performance of his life to send seven-time champion Roger Federer crashing out of the Dubai Tennis Championships on Wednesday.
The prospects for Donskoy had looked bleak as Federer dominated the opening set, but the world number 116 mounted a stunning comeback to defeat the 18-time grand slam champion 3-6 7-6 (9-7) 7-6 (7-5).
Federer took the first set in just 24 minutes, but Donskoy found some fight in the second and - after a brief power cut - the pair were soon locked in a tie-break, albeit after Donskoy had wasted a set point.
The Swiss was unable to stop his opponent levelling as he spurned three match points and in the decider he again struggled to kill the contest off despite taking a 5-2 lead.
Having forced another breaker Donskoy's battling qualities came to the fore again as he forced Federer into a number of errors, the latter a wide forehand that completed the 26-year-old's triumph.
Victory for Federer would have put a semi-final meeting with Andy Murray just one match away, but instead it will be either Donskoy or Lucas Pouille in the last four for the world number one.
World No. 116 Evgeny Donskoy saves 3 MPs in 2nd-set TB and rallies from 5-1 down in 3rd-set TB to upset 7-time #DDFTennis champion Federer.-- ATP Media Info (@ATPMediaInfo) March 1, 2017
Murray has faced little to worry him so far in United Arab Emirates with comprehensive victories over Malek Jaziri and Guillermo Garcia-Lopez.
The Spaniard was the latest to be dispatched as he struggled to put any pressure on Murray in their 73 minutes on court, the Briton winning eight games in a row to progress 6-2 6-0.
Next up for Murray - who hit 20 winners - is Philipp Kohlschreiber after he enjoyed a comfortable 6-4 6-4 win over Daniil Medvedev.
Pouille, the rising star of the ATP Tour, sent Romanian qualifier Marius Copil packing 6-1 6-4, while there were also a victory for Gael Monfils as he overcame a spirited Dan Evans 6-4 3-6 6-1.
Damir Dzumhur continued his impressive run with victory over Marcel Granollers - the Bosnian having beaten defending champion Stan Wawrinka in round one.
There was disappointment for two seeded players, though, as Tomas Berdych and Roberto Bautista-Agut bowed out of the tournament.
Bautista-Agut was beaten by fellow Spaniard Fernando Verdasco in three sets, while Berdych slumped to a surprise defeat against world number 66 Robin Haase, despite taking the first set.