Jan-Lennard Struff - also the doubles partner of Queenstown's Ben McLachlan - outlasted fourth seed Pablo Carreno Busta 7-6 (5) 6-7 (6) 7-6 (7) in an absolute thriller.
It a contest of brilliant skill and unbelievable drama, the world No 58 Struff eventually prevailed in three hours, converting his seventh match point.
Carreno Busta's exit means that for the first time since 1997, no seeds have made the semifinals.
It was a courageous display from world No 24 Carreno Busta, who saved six set points in the first set alone, before eventually succumbing.
He rebounded to take the second in a tie break, before a titanic third set struggle.
The Spaniard saved four match points – in scenes of incredible tension – to force a yet another tiebreak.
Both players had match points in the breaker, but in the end the German's prowess on serve (he hit 22 aces) and aggressive net rushing ultimately proved the difference.
Struff will face former Kiwi Cameron Norrie in the semifinal tomorrow.
