The Athletic has live coverage of the 2026 U.S. Open. NEW YORK — Félix Auger-Aliassime, the No. 3 seed at this year’s U.S. Open, bowed out in the second round Thursday afternoon after a sudden drop in intensity.Auger-Aliassime lost 6-7(5), 6-3, 6-2, 6-2 to Russia’s Karen Khachanov on Louis Armstrong Stadium. A year ago, the 26-year-old Canadian was a U.S. Open semifinalist, pushing world No. 1 Jannik Sinner in a close four-set match.One year later, the Canadian is out before the second week in Flushing Meadows, after losing to his fellow former semifinalist here.Auger-Aliassime began to experience physical issues halfway through the second set and couldn’t recover.“I just couldn’t feel well and was dizzy and seeing spots,” Auger-Aliassime said in a news conference. He said he will undergo testing, as he had never experienced something like this before on court. “This was abnormal a little bit, and there were no signs in the last couple of days and no signs this morning.”Khachanov said that he didn’t know if Auger-Aliassime was sick, injured or if the heat impacted him. But he did notice a dip in performance from his opponent which he seized on.“I noticed after the first set that he was down,” Khachanov said in a news conference. “I don’t want to take out the credit from myself because I was staying there fighting for three and a half hours, trying to bring the best effort.”The match had started strong for Auger-Aliassime. Despite losing a break advantage, Auger-Aliassime recovered to win the first-set tiebreak. But from there, Khachanov settled into the match. He began to hit with pace and confidence from the baseline, as Auger-Aliassime went 0 for 5 on break points in a set that was closer than the 6-3 scoreline.Why are some tennis players better at night?Tifo SportsAt 1-1 in the match, Auger-Aliassime’s level tumbled. In the third set, he tossed in five double faults, including one serving at *1-5 where the ball on the second serve landed on his side of the court, not even reaching the net. More concerning was how hampered he appeared in his movement, with heavy legs and little ability to push off on his serve.