BERLIN: Alexander Zverev became the latest big-name casualty to crash out of Halle's grass court tournament on Thursday, leaving world number seven Andrey Rublev as the only seeded player left in the draw.
After Roger Federer suffered a shock defeat on Wednesday, Zverev, who reached the semi-finals of the French Open last week, also exited in the second round when he lost 7-6 (7/4), 3-6, 6-3 to France's Ugo Humbert.
Along with Federer and Zverev, top seeds Daniil Medvedev, Roberto Bautista Agut, David Goffin and Gael Monfils also all failed to get past the second round in Halle.
"This is the biggest win of my career," Humbert, ranked 31 in the world, told Eurosport.
"I was mentally very stable, I kept pushing myself - it's something I have been working on."
In Friday's quarter-finals, the 22-year-old will face America's Sebastian Korda, who earlier edged out Kei Nishikori 2-6, 6-3, 7-5.
In the last eight, Rublev of Russia will face Germany's Philipp Kohlschreiber and 20-year-old Canadian Felix Auger Aliassime, who beat Federer over three sets, will play American qualifier Marcos Giron.
South Africa's Lloyd Harris, who beat Lukas Lacko of Slovkia 6-3, 7-6 (10/8), will play Goergia's Nikoloz Basilashvili or French qualifier Arthur Rinderknech for a place in the semi-finals.