"I had a problem seeing the ball since I only play under the lights once or twice during the year," the Czech Republic's No 1 woman said. "I knew she was a tough player and has a good record against top players. I wasn't going for my first serves and was missing many overheads and easy volleys."
Arantxa Sanchez Vicario, the No2 seed, and the fourth seeded Conchita Martinez both scored third-round victories on a chilly Florida afternoon to move into the quarter-finals.
Sanchez Vicario won 6-3, 1-6, 6-4 against the 16th seed, Ruxandra Dragomir of Romania. Sanchez Vicario has not won a trophy since May 1996 in Hamburg, Germany.
The sixth-ranked Martinez had a 6-3, 6-3 victory over Chanda Rubin, ranked 30th, in 65 minutes.
Steffi Graf's expected showdown with her successor as the world-ranked No 1, Martina Hingis, has been delayed by Graf's knee injury. Graf has pulled out of this month's tournament in Hamburg, where she could have faced Hingis, who is unbeaten this year.