Kerber has been scheduled to play Croatian qualifier Mirjana Lucic. She withdrew from the event to prepare for the U.S. Open, which begins Aug. 27.
Lucic eliminated Britain's Emily Webley-Smith 6-1, 6-2 in 46 minutes.
Second-seeded Serbian Jelena Jankovic had to stage a comeback to get past Kazakhstan's Yaroslava Shvedova 6-7 (7-9), 7-6 (7-4), 6-1.
No. 3 seed Roberta Vinci of Italy dropped Su-Wei Hsieh 6-2, 6-2 and No. 6 seed Peng Shuai of China eliminated Ayumi Morita of Japan 4-6, 6-0, 6-3.
French qualifier Pauline Parmentier, New Zealand's Marina Erakovic, qualifier Eugenie Bouchard of Canada and qualifier Casey Dellacqua of Australia also advanced Monday.
Astronomers offer more expansive view of universe
McPhee, Cokas 'working on their marriage' after affair