Vera Zvonareva avoided becoming the latest upset loser Wednesday and Venus Williams withdrew during surprising second-round action at the U.S. Open.
Williams, unseeded in the final major event of the year but considered a threat after recovering from hip and abdominal injuries this summer, pulled out of her match against No. 22 seed Sabine Lisicki.
Williams, a two-time winner of this tournament, said in a statement she had recently been diagnosed with an autoimmune disease that brings about fatigue and joint pain.
"I'm really disappointed," she said in the statement. "I enjoyed playing my first match here and wish I could continue, but right now I am unable to. I am thankful I finally have a diagnosis and am now focused on getting better and returning to the court soon."
Zvonareva, seeded second, survived a difficult match against Kateryna Bondarenko and advanced with a 7-5, 3-6, 6-3 victory.
In the 16 women's matches played Wednesday, however, players seeded eighth, 12th, 14th and 20th were eliminated.
No. 8 Marion Bartoli fell to Christina McHale 7-6 (7-2), 6-2; Angelique Kerber shocked No. 12 Agnieszka Radwanska 6-3, 4-6, 6-3; Irina Falconi was a 2-6, 6-3, 7-5 winner over No. 14 Dominika Cibulkova; and No. 20 Yanina Wickmayer retired in the second set and thus fell victim to Alla Kudryavtseva.
Alexandra Dulgheru, who had knocked out Wimbledon champion Petra Kvitova in the first round, lost to Monica Niculescu 6-3, 6-0.
Samantha Stosur, seeded ninth, put an end to the brief run of success for Coco Vandeweghe with a 6-3, 6-4 victory. Vandeweghe had recorded her first grand slam match victory in seven tries in the opening round.