Only one of the seeded players on Tuesday's nine-match schedule was able to advance, with fourth-seeded Ekaterina Makarova, No. 7-seeded Iveta Benesova and ninth-seeded Barbora Zahlavova Strycova joining Pironkova as upset victims.
Fifth-seeded Sara Errani bucked that trend in a 6-1, 6-0 win over Maria-Teresa Torro-Flor. Errani placed 80 percent of her first serves and won 70 points of the points on serve and 61 percent when Torro-Flor served.
Alberta Brianti's win over Pironkova was nearly as one-sided, as she won 6-1, 6-2 and converted all six of her break-point chances.
Makarova was beaten 7-6 (7-4), 6-3 by Mirjana Lucic while Lucia Hradecka topped Benesova 6-4, 6-4 and Laura Pous Tio was a 6-3, 6-3 winner over Zahlavova Strycova.
Other first-round winners Tuesday were Virginie Razzano, Polona Hercog, Varvara Lepchenko and Gisela Dulko.