He somehow dug it out about eight feet short and holed the clutch putt for a par, while Na saw his mid-range effort for a four at the last finish agonisingly on the edge of the cup.

BBC: Ernie Els completes Arnold Palmer Invitational victory

Third seed Daniel Hantuchova, of Slovakia, gained a 6-2 6-4 victory over Olga Govortsova, of Belarus, while fourth seed Na Li , of China, overcame Russian Yaroslava Shvedova 4-6 6-2 6-0.

BBC: SPORT | Tennis | Cavaday claims second-round spot

Petrova won her first-round tie against compatriot Elena Vesnina, triumphing 4-6 6-2 6-3, while Chinese 13th seed Li Na beat Spain's Beatriz Garcia Vidagany 6-0 6-2 to set up a clash with Slovakia's Dominika Cibulkova.

CNN: Serena survives epic in Madrid opener

Russian No. 2 Sharapova will play 20th-seeded compatriot Maria Kirilenko, while the remaining quarterfinal tie pits China's French Open champion Li Na against German No. 18 Angelique Kerber.

CNN: STORY HIGHLIGHTS

Fourth seed Agnieszka Radwanska eased past Irina-Camelia Begu, while there were also wins for German fifth seed Angelique Kerber and China's sixth seed Li Na .

CNN: Sharapova to face Venus in crunch clash