Vinci dropped her serve four times but survived with a 6-1, 1-6, 6-4 win over Nina Bratchikova. Bratchikova, No. 108 in the world, lost to Vinci 7-5, 7-5 earlier this year in their only other meeting.
Vinci started strong, not facing a break point in the first set, even though her serve was shaky throughout. She was good on just 53 percent of her first serves but was solid in the return game, cashing in five of her 10 break-point chances.
No. 7-seeded Nadia Petrova won the first 11 games of a 6-0, 6-1 rout of Barbara Luz. Petrova won 67 percent of the points on serve and 65 percent when receiving.
Carla Suarez Navarro defeated Olga Govortsova 6-4, 6-4 and Silvia Soler-Espinosa beat Sorana Cirstea by the same 6-4, 6-4 score.