Stefanos Tsitsipas crashed out of the Vienna Open after losing in a dramatic third-set tie-break against Borna Coric, who claimed his third successive win over the Greek ace.
The second seed was the highest-profile casualty in the Austrian capital on Thursday, as he succumbed to the Croatian once more 4-6 6-4 7-6 (7-4).
Coric rescued six match points before stunning Tsitsipas at the 2020 US Open, while he also triumphed when they collided in the Cincinnati showpiece in August.
The world number 27's chances of completing a hat-trick of victories appeared bleak at a set and break down, but he rallied to force a decider that went the distance, before holding his nerve for another notable win.
Coric's reward is a quarter-final clash with Hubert Hurkacz, who boosted his chances of qualifying for next month's ATP Finals with a 7-5 4-6 6-3 win over Emil Ruusuvuori.
Daniil Medvedev advanced to the last eight after a 6-3 6-3 victory over home favourite Dominic Thiem. Next up for the top seed is Jannik Sinner after the Italian saw off Francisco Cerundolo 7-5 6-3.
Third seed Andrey Rublev's ATP Finals hopes were dented after a 6-3 6-4 defeat by Grigor Dimitrov, who will play Marcos Giron after the American overcame seventh seed Cameron Norrie in straight sets.
Over in Basel, third seed Felix Auger-Aliassime required just 49 minutes to complete a commanding 6-1 6-0 rout of Miomir Kecmanovic for his 10th straight ATP win.
Meanwhile, Stockholm champion Holger Rune continued his momentum by recording a seventh straight victory after seeing off Ugo Humbert 6-4 6-2.
Sixth seed Roberto Bautista Agut enjoyed a straight-sets win over three-time grand slam champion Andy Murray to set up a clash with home favourite Stan Wawrinka, who outlasted Brandon Nakashima in a deciding set.