China's fifth-seeded Li Na smacked 19 winners and fought off a late comeback bid to defeat American Varvara Lepchenko 6-2, 6-4 on Saturday to reach the fourth round of the WTA and ATP Miami Masters event.
Li had been sidelined for seven weeks after hurting her left ankle in the Australian Open final, which she lost to Victoria Azarenka.
With her second victory at the $8.5 million hardcourt event, she improved to 16-2 this season and booked a round-of-16 date with the winner of a later match between Danish ninth seed Caroline Wozniacki and Spain's Garbine Muguruza.
Lepchenko made 19 unforced errors in falling to 4-7 for the season.
Li dominated the opening set, dropping only five points on her serve while Lepchenko managed only one winner against 10 unforced errors.
Li jumped ahead 4-2 in the second set before Lepchenko managed her first break-point chance. The American took advantage with a net cord winner to break back and then held to level the set at 4-4.
After holding, Li ended matters in the 10th game. Lepchenko hit a backhand winner and Li netted a backhand attempt on the Chinese star's first two match points but Li smashed a forehand winner on her third match point for the victory.
On the men's side, French eighth seed Richard Gasquet dispatched Belgian Olivier Rochus 7-5, 6-2 to reach a third-round match against either Taiwan's Lu Yen-Hsun or Russia's Mikhail Youzhny.
US 17th seed Sam Querrey rallied to eliminate Poland's Lukasz Kubot 4-6, 6-3, 6-3 in one hour and 47 minutes. Querrey will next face either Canadian 14th seed Milos Raonic or Frenchman Guillaume Rufin.
Belgium's David Goffin ousted German 15th seed Philipp Kohlschreiber 7-6 (7/5), 4-6, 6-2. Next in Goffin's path will be the winner of a later match between Spanish 10th seed Nicolas Almagro and Argentina's Guido Pella.
Other later men's matches send British second seed Andy Murray against Australian Bernard Tomic and Czech fourth seed Tomas Berdych against Spain's Daniel Gimeno-Traver.
Later women's matches will send World No. 1 Serena Williams against Japan's Ayumi Morita and Venus Williams against fellow American Sloane Stephens.