Russian veteran Karen Khachanov defeated third-seeded Felix Auger-Aliassime Thursday in the second round of the US Open in four sets.
Khachanov, unseeded this year but a familiar face in the latter stages of big tournaments, beat Auger-Aliaissime 6-7 (5/7), 6-3, 6-2, 6-2.
The 26-year-old Canadian, a two-time semifinalist at Flushing Meadows, eked out a first-set tiebreaker against the hard-hitting Russian, who himself made the US Open semifinals in 2022.
But Auger-Aliassime, who appeared to give up quickly on some balls, was undone by a rash of unforced errors in the subsequent sets. He made 47 in all, compared with 30 for Khachanov.
Khachanov also won several key points with blistering backhand down-the-line winners.
"Maybe he had some physical issues," Khachanov told an on-court interview. "It's part of our sport. It's part of tennis."
"I tried to give my best performance. Fight," Khachanov said. "I'm super happy to get this win."
After reaching the quarterfinals of the French Open and Wimbledon, Auger-Aliassime withdrew from the Rogers Cup in Montreal in early August due to a back injury. He won two matches at the Cincinnati Open in mid-August, but lost in the round of 16 to Frances Tiafoe.
Auger-Aliassime entered this year's US Open without a coach after parting ways with long-time coach Frederic Fontang in July.
The Canadian's exit follows that of 24-time Grand Slam champion Novak Djokovic, the fourth seed who fell in the first round.