Just over two hours into the U.S. Open, two of the top seven women are already out.

Seventh-seeded Ana Ivanovic lost her first-round match Monday, but it wasn't much of an upset. She had a tough draw against Dominika Cibulkova, a former top-10 player and Australian Open runner-up whose ranking had fallen to 50th because of injury.

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Cibulkova won 6-3, 3-6, 6-3 in the tournament's first match at Arthur Ashe Stadium. She had undergone surgery on her left Achilles in February and missed more than four months.

Ivanovic, the 2008 French Open champ and a former No. 1 player, was one of the few women in the field who have defeated Serena Williams in a Grand Slam match, beating her at the 2014 Australian Open. Cibulkova went on to reach the final at that tournament, losing to Li Na.

Cibulkova was the seeded player being upset in the first round of the past two U.S. Opens, including a loss to 15-year-old American CiCi Bellis a year ago.

Third-seeded Maria Sharapova withdrew from the U.S. Open on Sunday because of a lingering right leg injury.