NEW YORK - French Open champion Maria Sharapova and Australian Open winner Stan Wawrinka survived some shaky moments Wednesday to book their third-round berths at the US Open. Sharapova, who lifted her fifth Grand Slam title at Roland Garros this year, fought back from a set down in a gritty 4-6, 6-3, 6-2 win over 95th-ranked Romanian Alexandra Dulgheru. The fifth-seeded Russian was reluctant to blame the windy conditions in the cavernous Arthur Ashe Stadium court for her difficulties, which included 46 unforced errors.And after two hours and 26 minutes on court -- in a match that began in hot sunshine and ended under the floodlights -- she had her 17th three-set win of the season, the most on the WTA Tour. "It was difficult," Sharapova said. "Obviously the conditions were tough. You start in the sun, you finish under the lights. "Overall I felt like in the end I was in much better shape than she was and I could have played another few sets. Mentally that helped me a lot."Sharapova and Wawrinka were the day's headliners as two-time defending women's champion Serena Williams and the top men Novak Djokovic, Roger Federer and Andy Murray all had the day off. Wawrinka, the third seed from Switzerland, turned back the challenge of Brazilian left-hander Thomaz Bellucci 6-3, 6-4, 3-6, 7-6 (7/1) to become the first men's seed into the third round. Wawrinka was untouchable on his serve through two sets, not facing a break point until Bellucci broke him twice to take the third.The Brazilian broke Wawrinka in the third game of the fourth, but the Swiss broke back to knot the set at 3-3. After holding at love for a 5-4 lead, Wawrinka had two match points against Bellucci's serve in the 10th game but couldn't convert either. He grabbed the tiebreaker by the throat, however, and finished it off with a service winner after two hours and 36 minutes with the hands of the clock creeping toward 1 am. "I was playing really well," Wawrinka said of his sparkling start. "I was really aggressive and serving really well. When you drop your level a little against Bellucci, it's tough. He starts to play better."The tension seemed to get to Wawrinka at least briefly when he told one loud courtside fan to shut-up. But he was able to get back on the attack. "The fourth set I tried to focus on my game," he said. "I was more aggressive at the end of the match." Most of Wednesday's men's action was wrapping up the first round, and the exits of Steve Johnson and Ryan Harrison meant just three American men reached the second round -- the fewest in US Open history. American women were keeping the home flag flying, and five-time Grand Slam champion Venus Williams did her part.The two-time winner, who hadn't made it past the second round the past three years, reached the third round with a 6-1, 6-4 victory over Timea Bacsinszky. Fourth-seeded Pole Agnieszka Radwanska became the tournament's biggest upset victim, falling 6-3, 6-4 to China's Peng Shuai. Peng avenged a loss to Radwanska at the 2011 Australian Open where the Chinese player had held two match points. Poland's Radwanska, a former Wimbledon finalist who counts this year's Australian Open among two other Grand Slam semi-final spots, was left to ponder why she has never made it past the last 16 in nine US Open appearances.World number two Simona Halep needed less than an hour to book her third-round berth, with a 6-2, 6-1 victory over Slovakian Jana Cepelova. Halep was broken early to trail 0-2, but won 12 of the next 13 games to secure the win. Sixth-seeded German Angelique Kerber also advanced on cue, downing Russian Alla Kudryavtseva 6-2, 6-4. Men's sixth-seed Tomas Berdych of Czech Republic brought Lleyton Hewitt's 62nd Grand Slam appearance to a quick end, downing the former world number one, and 2001 champion, 6-3, 6-4, 6-3.Seventh-seeded Bulgarian Grigor Dimitrov finally ended his US Open jinx. After coming up empty in three straight appearances, he defeated US wildcard Harrison 6-2, 7-6 (7/4), 6-2. South African Kevin Anderson rallied from a break down in the final set to defeat Uruguay's Pablo Cuevas 6-3, 6-7 (3/7), 4-6, 6-2, 7-6 (7/1) in just over four hours. But three men's matches were cut short by injury retirements.Wimbledon quarter-finalist Marin Cilic of Croatia advanced when a right ankle injury forced Cypriot Marcos Baghdatis to retire while trailing 6-3, 3-1. Spain's Feliciano Lopez advanced when Croatian Ivan Dodig retired with cramping and muscle cramps also left Johnson unable to continue against Japan's Tatsuma Ito.