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