Former world number one Marat Safin stumbled out of the Paris Masters when he lost 6-0, 7-6 to Argentine qualifier Juan Monaco in the first round on Monday.
The Russian, three-time winner of the Paris indoor tournament, picked up his game too late to unsettle Monaco, who will next meet France's Gael Monfils, seeded 16th.
"I didn't take my chances and that's why the score is 6-0, 7-6," Safin told reporters, adding he is thinking over his future in the game.
"I need to think it through. If I feel like I want to continue to play, I will. If no, it will be over," he said.
"For the moment, I just need to rest."
Safin lost the first eight games and notably served four double faults in a single game as Monaco cantered through the match.
The former US and Australian Open champion got himself together at 2-0 down in the second set, and double faults turned into aces.
Safin broke back for 2-2 and both players then held serve until the tiebreak, which Monaco took 7-4 when Safin sent a forehand long.
Russian Igor Andreev, ranked 20th in the world, beat France's Paul-Henri Mathieu 7-6, 6-3 and will take on local favourite and Masters Cup hopeful Gilles Simon in the second-round.
Earlier, American Sam Querrey benefited from Marcos Baghdatis's retirement with back pain to set up a second-round meeting with world number four Andy Murray of Britain.
"I felt a sharp pain in the back and I did not want to take any risk," said the Cypriot, who was 5-7, 7-6, 3-2 down when he called for the trainer.
Czech Tomas Berdych also reached the second round with a 6-4, 7-5 victory over American Robby Ginepri.
Berdych, winner of the Paris indoor tournament in 2005, will next meet Swiss 12th seed Stanislas Wawrinka, who still has an outside chance of grabbing one of the three remaining spots for the season-ending Masters Cup in Shanghai.
Although he dropped serve twice in the match, Berdych broke twice in each set to ease past Ginepri.
German Nicolas Kiefer resisted Croatian Ivo Karlovic's 12 aces to win 6-4, 7-5 and set up a second-round encounter with defending champion David Nalbandian, seeded eighth and also looking for a Masters Cup berth.
Another Croatian, Marin Cilic, saw off Italy's Andreas Seppi 7-6, 6-2 and will take on Spanish qualifier Marcel Granollers.