Second seed Roberto Bautista Agut became a Wednesday upset victim at the Gstaad Open as he was sent out 6-2, 6-4 by 100th-ranked Frenchman Arthur Rinderknech in the second round.
The outsider earned the top win of his career as his ninth of the season a week after reaching the Bastad quarter-finals.
Rinderknech now owns two Top 20 upset wins after beating Jannik Sinner in Lyon in May.
The French player next takes on Laslo Djere in a fourth quarter-final of 2021.
Serb Djere, seeded seventh earned his spot over qualifier Zizou Bergs 6-2, 4-6, 6-2 in two hours.
Fifth seed Federico Delbonis was knocked out 6-0, 6-7(2), 7-6(3) by France’s No. 155 Hugo Gaston after almost two and a half hours.
Gaston will face fourth-seeded Chilean Cristian Garin, who defeated Australian Marc Polmans with the loss of just three games in the opening set in a rout which took 54 minutes.
Garin, winner of five clay titles, likened the high-altitude clay of this VIP village to Santiago, where he won the tournament in March.
”I have a good feeling about playing in high altitudes so I am really happy,” the South American said.
Top seed Denis Shapovalov, a Wimbleodn semi-finalist, and No. 3 Casper Ruud, last week’s Bastad champion begin the week with their second-round matches here on Thursday.