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.