Roger Federer lost his comeback match after two months away, falling to Pablo Andujar 6-4, 4-6, 6-4 Tuesday in the second round of the Geneva Open.
Federer's first match on clay in almost two years kept him on court for almost two hours in only his second tournament since the 2020 Australian Open. The past 15 months have included two surgeries on his right knee.
In the decisive set, the top-seeded Federer forced a service break and led 4-2 before Andujar rallied.
Federer saved two match points on his own serve, but the third ended with a wayward forehand under pressure on the baseline.
Andujar put his hands to his head after clinching victory and exchanged an almost apologetic smile with Federer at the net.
The 39-year-old Federer and 35-year-old Andujar were playing each other on tour for the first time.
Before going on court, Federer was a spectator for part of the ATP Tour debut of perhaps the best prospect in Swiss men's tennis since his own rise in the 1990s.
With Federer watching some of the match, 18-year-old Dominic Stephan Stricker beat former U.S. Open champion Marin Cilic 7-6 (5), 6-1 in the first round.
Stricker, last year's French Open junior champion, is ranked 419th. Cilic, who won his only Grand Slam singles title in 2014, is ranked 46th.
The Swiss left-hander had nine aces and no double-faults. He broke Cilic's serve four times and was broken only twice.
"I was getting nervous," Stricker said. "It was actually OK until 5-1, 30-love. I was happy to finish it at 6-1 and not serve again."
Stricker has practiced previously with Federer. His next opponent will be 40th-ranked Marton Fucsovics, who beat Swiss qualifier Henri Laaksonen 7-5, 7-5.