Jill Craybas, a late replacement for Jennifer Capriati, moved into round two of the Pacific Life Open with a 6-1 3-6 6-2 win over Belgium's Els Callens. With the top 32 seeds all given a bye into the second round, Craybas will now face 11th seed Conchita Martinez.
Elsewhere, there were straight-set wins for Italy's Antonella Serra Zanetti over Rita Grande and Anna-Lena Groenefeld over Virginia Ruano Pascual.
Austria's Barbara Schett saw off Tatiana Perebiynis 6-7 6-1 6-2.
Jamea Jackson was taken off court in a wheelchair with heat exhaustion in her match against Marissa Irvin.
"I couldn't move," said Jackson.
"I couldn't swing. I was terrified I was going to get a full body cramp. I've had one of those, and it was the worst feeling I've ever had in my entire life."