Belgians Kim Clijsters and Justine Henin made winning starts to their campaigns at the Sony Ericsson Open in Miami on Friday.
Clijsters is playing for the last time in Miami
Clijsters continued her final season before retirement with a bizarre 4-6 6-0 6-0 win over Akiko Morigami.
Second seed Henin survived a shaky start to beat Vania King 6-4 6-1 and reach the third round.
The world number one, who won titles in Dubai and Doha last month, admitted she was lacking match fitness.
"I wasn't at my best, far from that - I need some matches," said Henin.
"Conditions were tough, pretty windy and hot, and I needed a little time to get used to them. The second set was much better, but I need to improve."
Henin has never gone beyond the quarter-finals in Miami, reaching the last eight in 2003 and 2005.
"I've never played very well here in the past, but the past is the past," said Henin.
In other second-round matches, Serbian seventh seed Jelena Jankovic beat Peng Shuai of China 6-2 6-4, and Dinara Safina, the Russian 10th seed, eased to a 6-1 6-1 win over America's Laura Granville.
Sixth-seeded Russian Nadia Petrova also advanced, beating France's Nathalie Dechy 6-4 3-6 7-6 (7-2).
And Daniela Hantuchova, the winner in Indian Wells last week, beat Michelle Larcher de Brito 7-5 6-0.