NEW YORK -- Sixth-seeded Caroline Wozniacki held off qualifier Duan Ying-Ying to win her first-round match at the U.S. Open.

With boyfriend Rory McIlroy in the stands, Wozniacki fought off a set point in the second to win 6-2, 7-5 on Tuesday.

The 133rd-ranked Duan had a chance to serve out the set at 5-3 in her Grand Slam debut. But the 2009 U.S. Open finalist broke back. Then Duan had a set point on Wozniacki's serve that she couldn't convert.

Wozniacki broke serve in the next game, then staved off three break points to clinch the win.