( 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 .
Tropical Storm Irene champion Petra Kvitova goes out in third round of U.S. Open . Czech is beaten in straight sets by Britain 's Maria Sharapova . Maria Sharapova taken to three sets by U.S. 's Heather Watson .