World number two Li Na advanced to the third round of the Sony Open without hitting a ball when Russia's Alisa Kleybanova withdrew from Friday's clash due to illness.
After a first round bye, the Australian Open winner was supposed to lead off what has been dubbed the 'parade of champions' on the Crandon Park centre court.
But Kleybanova, who is fighting her way back up the rankings after battling Hodgkin's lymphoma, handed her Chinese opponent a walkover due to a viral infection.
Slovakian 10th seed Dominika Cibulkova, who lost the Australian Open final to Li, sped past Austria's Yvonne Meusburger 6-1 6-2 to reach the third round.
However Italian Roberta Vinci, the 13th seed, was beaten 6-4 2-6 7-5 by Czech Barbora Zahlavova Strycova, while 18th seed Eugenie Bouchard collapsed after a strong first set, losing 1-6 6-1 6-2 to Elina Svitolina.
There was also an early exit for Jelena Jankovic, the seventh seed going down 6-3 2-6 7-6 (7-2) to American Varvara Lepchenko.
Venus Williams was not at her fluent best but was still a comfortable 6-3 6-3 winner over Anna Schmiedlova. The three-time former champion will next face face Australian wild card Casey Dellacqua, who saw off Jana Cepelova - a late call-up for the injured Simona Halep - 6-4 1-6 6-4.
Sloane Stephens was another American to progress, winning 7-5 6-3 against Zarina Diyas of Kazakhstan.
Alize Cornet went the distance before beating Andrea Petkovic 6-2 6-7 (0/7) 6-4, Kaia Kanepi was too good in tie-breaks for Christina McHale, winning 7-6 (7/5) 7-6 (7/0) and there were also wins for Ajla Tomljanovic, Elena Vesnina and Carla Suarez Navarro.