Kim Clijsters was outplayed by her fellow Belgian Yanina Wickmayer who put an early end to the two-time former champion's campaign at the Sony Ericsson Open today.
Having missed large chunks of the 2011 season with injury and also been sidelined since the Australian Open in January due to an ankle complaint, Clijsters has seen her ranking drop to the point where she is unseeded at this fortnight's event in Key Biscayne, Miami.
The 28-year-old former world number one strung together hard-earned wins over Jarmila Gajdosova and Julia Goerges in the opening two rounds but found Wickmayer too tough in the last 32, sliding to a 6-4 7-6 (7/5) defeat.
That meant a first victory for 22-year-old Wickmayer over her illustrious countrywoman, who has lost the Belgian number one ranking to her younger rival, at least temporarily. It was just their second meeting on the WTA Tour.
Awaiting Wickmayer in the fourth round will be Denmark's Caroline Wozniacki, who like Clijsters is a former world number one, knocked down to sixth since the start of the year.
Wozniacki, who is the fourth seed, rolled past Petra Cetkovska of the Czech Republic, winning 6-3 7-5,
Tenth seed Serena Williams had little trouble in beating Italy's 21st seed Roberto Vinci 6-2 6-1 in just over an hour.
The American punished her opponent's second serve, breaking five times on the way to a routine win.
Chinese eighth seed Li Na saw off Czech player Iveta Benesova 7-5 6-2.
Twelfth-seeded German Sabine Lisicki was a 6-4 7-5 win over Chinese 17th seed Peng Shuai, while Russia's Ekaterina Makarova saw off Germany's Mona Barthel 6-2 6-4.
Russian Maria Sharapova, the second seed, rolled past 19-year-old American Sloane Stephens 6-4 6-2.
Reigning US Open champion Samantha Stosur will face Williams in the fourth round after the Australian beat South Africa Chanelle Scheepers 2-6 7-5 6-2 in the final match of the day.