( CNN ) -- Wimbledon champion Petra Kvitova crashed out and Maria Sharapova survived an almighty scare on the opening day of the U.S. Open Monday . Kvitova , who beat Sharapova in the final at Wimbledon , exited to Romanian Alexandra Dulgheru in straight sets , 7-6 6-3 . Sharapova , second favorite behind Serena Williams to win the final grand slam of the season , flirted with defeat before seeing off British teenager Heather Watson , 3-6 7-5 6-3 . 19-year-old Watson led by a set and a break before Sharapova fought back to force a decider . An early break gave the Russian third seed the cushion to wrap up victory , but it was hardly a convincing performance . Kvitova had been set to open on the main Arthur Ashe stadium court , but organizers switched her to the smaller Louis Armstrong court as they made changes to the schedule after Tropical Storm Irene blew through New York over the weekend . 49th-ranked Dulgheru never looked back after taking the first set tiebreaker 7-3 and broke her Czech opponent to lead 5-3 in the second set before serving out for victory to love . Kvitova is the first reigning Wimbledon champion to lose in the first round of the U.S. Open in the Open era . By contrast , second seed Vera Zvonareva of Russia enjoyed an easy passage to the second round as she beat Stephanie Foretz Gacon of France , 6-3 6-0 . Two-time champion Venus Williams , who is not seeded this year , opened her campaign in the night session at Flushing Meadows with a 6-4 6-3 win over Vesna Dolonts of Russia .
Wimbledon champion Petra Kvitova goes out in first round of U.S. Open . The Czech Republic will play the winner of Sunday's women's singles final between American Sloane Stephens and Russian Maria Kirilenko. Maria Sharapova taken to three sets by Britain 's Heather Watson .