Updated

Ninth seed Angelique Kerber of Germany rallied to win her first-round match and American Venus Williams breezed into the second round Monday at the $2.369 million Western & Southern Open tennis event.

Kerber, last year's finalist, disposed of Italian Karin Knapp, 6-7 (6-8), 6-0, 6-1.

Williams, playing in only her second event since a first-round loss at the French Open, carved up a 6-4, 6-1 victory against Slovakian qualifier Jana Cepelova. Williams has been hampered by a low back injury this year, but she moved into round two in a swift 66 minutes.

Former U.S. Open champion Samantha Stosur posted a first-round victory. The 11th-seeded Aussie got past former top-five Russian star and fellow former U.S. Open winner Svetlana Kuznetsova, 6-1, 7-5, on the hardcourts at the Lindner Family Tennis Center.

Stosur was a hardcourt titlist in Carlsbad, Calif., two weeks ago.

Italian Roberta Vinci, the No. 12 seed, ousted American wild card Bethanie Mattek-Sands, 6-4, 5-7, 6-3.

Meanwhile, 16th-seeded Russian Maria Kirilenko outlasted Georgian qualifier Anna Tatishvili, 4-6, 7-6 (7-4), 7-6 (7-4).

In action involving Americans on Day 1, Sloane Stephens held off Croatian qualifier Petra Martic 6-2, 3-6, 6-3, qualifier Vania King topped France's Kristina Mladenovic 6-3, 6-4, and wild card Lauren Davis surprised Czech veteran Klara Zakopalova 7-6 (7-3), 7-6 (7-1). Stephens is rewarded with a second-rounder against 2011 champion, 2010 runner-up and former world No. 1 Maria Sharapova, while King will meet former top-ranked star Victoria Azarenka in her next outing.

Also advancing were qualifiers Marina Erakovic of New Zealand and Eugenie Bouchard of Canada, Russian Alisa Kleybanova and Romanian Simona Halep, who has won three WTA titles since mid June. Up next for Halep will be Wimbledon champion Marion Bartoli.

This week's top seed is last week's Toronto titlist, Serena Williams, who's also the reigning U.S. and French Open champ.

China's Li Na beat Kerber in last year's Western & Southern finale. Li will meet Davis in the round of 32 here.

This week's winner will earn $426,000. The tournament is part of the U.S. Open Series, or the North American hardcourt events that lead up to the U.S. Open, which will commence August 26.