Bouchard retires from opening match at China Open

BEIJING (AP) A teary-eyed Eugenie Bouchard retired from her opening match against Andrea Petkovic at the China Open due to dizziness on Monday, her first match since falling at the U.S. Open last month and suffering a concussion.

Bouchard slipped in the locker room after her third-round win against Dominika Cibulkova at the U.S. Open, falling backward and landing hard on the back of her head. She was forced to withdraw from the tournament, as well as subsequent tournaments in Tokyo and Wuhan.

The Canadian was trailing 6-2, 1-1 against Petkovic on Monday when she decided to call it quits.

''I just asked her what happened, and she told me that she felt very dizzy,'' Petkovic said after the match. ''Then I asked if it was the same, if it still was the concussion. She said, `Yeah, it tends to come back when she gets physically very active.'''

It's been a difficult year for the Canadian following her breakout season in 2014 when she reached the Wimbledon final and the semis at the Australian and French Open. Her record in 2015, meanwhile, is just 12-17 and her ranking has fallen all the way from No. 5 to No. 38.

Bouchard's retirement came on the heels of four other withdrawals in the women's draw on Sunday, including top-seeded Simona Halep, who retired from her match against Spain's Lara Arruabarrena with a recurring Achilles injury.

Defending champion Maria Sharapova and world No. 1 Serena Williams also withdrew before the tournament began, citing injuries.

In women's second-round matches on Monday, U.S. Open runner-up Roberta Vinci of Italy defeated Alison Van Uytvanck of Belgium 6-2, 6-2, Madison Keys of the United States rallied to beat Kateryna Bondarenko of Ukraine 3-6, 6-1, 6-0, and seventh-seeded Carla Suarez Navarro ousted Puerto Rico's Monica Puig 7-6 (1), 6-2.

In a first-round match, Switzerland's Belinda Bencic outlasted Madison Brengle of the United States 6-7 (4), 6-4, 6-3.

In the men's draw, eighth-seeded Jo-Wilfried Tsonga of France was upset by Austria's Andreas Haider-Maurer 7-6 (4), 6-2.

Tsonga said afterward that he, too, felt dizzy during the match and he was asked if the heavy pollution in Beijing on Monday had affected his play. According to the U.S. Embassy's air quality measurements, the PM 2.5 reading hit 292 in the late afternoon, which is considered ''very unhealthy'' on the index.

''I don't know. You know, nothing in me can calculate if it's enough oxygen for me or not,'' he said. ''Today I had an opponent, he was just better than me today.''

In other first-round matches, Belgium's David Goffin, the seventh seed, defeated Italy's Andreas Seppi 6-2, 6-3, Fabio Fognini of Italy beat Slovakia's Martin Klizan 6-2, 6-1, and Chinese wild card Zhang Ze, ranked No. 219 in the world, beat 70th-ranked Denis Istomin of Uzbekistan 6-3, 1-6, 6-3.