Top seed Dominic Thiem beat Aljaz Bedene 7-5, 6-4 to book a place in the Qatar Open quarterfinals as all his fellow seeds bowed out in the second round in Doha on Wednesday.
Slovenian Bedene saved 12 out of 15 break points to push the Austrian but the world number five survived the test to be the only seed left in the draw, apart from Frenchman Richard Gasquet, who won the event in 2013.
Yet world number 31 Gasquet, the fifth seed, was surprisingly beaten 6-3, 6-4 in the late match by Greece's rising talent Stefanos Tsitsipas, with the 19-year-old from Athens progressing to face Thiem in the next round.
Seventh-seeded Fernando Verdasco was defeated 6-4, 3-6, 6-4 by Russian youngster Andrey Rublev while eighth seed Feliciano Lopez suffered a shock 6-4 7-6(2) loss to Bosnia's Mirza Basic, who is ranked 138th in the world.
The Spanish duo joined high-ranking players Pablo Carreno Busta, Tomas Berdych, Albert Ramos-Vinolas and Filip Krajinovic in exiting the tournament in the early stages.
In the quarter-finals, Rublev, 20, will face Croatia's Borna Coric, who ousted Carreno Busta in the first round, while Basic will take on Guido Pella after the Argentine overcame Stefano Travaglia 7-6(4) 6-3.
French wildcard Gael Monfils beat Jan-Lennard Struff 6-3 1-6 6-3 to set up the other last-eight clash with German Peter Gojowczyk.