NEW YORK // Jelena Jankovic looked a far cry from a woman seeded second in the early stages of a grand slam tournament, yet overcame her physical fragility and the challenge of Sofia Arvidsson to win in three sets at the US Open. The Serb beat the Swede 6-3, 6-7 (5), 7-5 to progress to the third round, but she is showing slow signs of recovery from the persistent knee injury that has affected her since Wimbledon. Jankovic's lack of conditioning was evident throughout the two-hour, 44-minute match - at one point in the final set she slumped face down on the court for several moments. "I was just tired, and I couldn't get up," she said. "I was so exhausted at that moment. I was breathing hard, and I didn't have the energy to get up. "For me to play three hours, it's amazing at this moment, because I haven't been training as hard as I want to," Jankovic said. "I'm now training to get that, but it takes time. It's not going to happen overnight." She planned to run on a treadmill for 10 minutes after the match but lasted only three before her leg cramped up. "I was lucky," she said. "I was saying to my coach, 'Can you imagine if this happened during the match? I probably wouldn't have been able to finish it.' Luckily, I finish before it happens. So just in time." Jankovic twice served for the match in the middle set against Arvidsson but could not put her opponent away. Even with the squandered break opportunities in the second set, Jankovic had a chance to close it out in the tiebreak but, after going to a 3-0 lead, she lost six straight points and the set. Jankovic held off Arvidsson in a back-and-forth third set when both had trouble holding serve. When Arvidsson fired long on the final point, Jankovic had her third service break of the set and eighth of the match. While Jankovic escaped an early exit, Eighth seed Vera Zvonareva did not. The Russian was upended by the Ukrainian Tatiana Perebiynis 6-3, 6-3 in the tournament's biggest upset so far. Svetlana Kuznetsova, seeded third, shook off an early break and rallied to a 7-6 (3), 6-1 victory over the Romanian Sorana Cirstea. Kuznetsova, the 2004 champion, trailed 4-2 in the opening set before getting back on serve and eventually forcing a tiebreak that she dominated against her inexperienced opponent. She cruised to a 5-0 lead in the second and closed out the match in one hour, 13 minutes. "Here you feel special, like I've made it here," Kuznetsova said. "It's an amazing feeling. ... I just play much more confident." No 5 seed Elena Dementieva of Russia advanced at the expense of France's Pauline Parmentier 6-2, 6-1. Marion Bartoli of France, Victoria Azarenka of Belarus and Patty Schnyder of Switzerland also won. Francesca Schiavone of Italy was knocked out by Britain's Anne Keothavong 6-2, 3-6, 6-4, and Spain's Anabel Medina Garrigues was the other seeded casualty, eliminated by Zheng Jie of China 6-1, 6-4.