Cirstea was on the court just more than an hour in a 6-1, 6-3 win over Anna Schmiedlova. She won two-thirds of the points on serve and saved all four break points she faced. Cirstea also took half of the points when Schmiedlova served.
Kimiko Date-Krumm battled sixth-seeded Garbine Muguruza for almost 3 hours before finishing off a 6-7 (2-7), 7-5, 7-6 (8-6) win. Date-Krumm, 43, dropped serve eight times but cashed in 9-of-21 of the break points she had against Muguruza, a player less than half her age and 70 places ahead of her in the rankings.
The Muguruza loss and the defeat Monday of No. 7-seed Bethanie Mattek-Sands were the only upsets of the first round. Seeded players went 3-1 Tuesday.
Fourth-seeded Ekaterina Makarova got by Olga Savchuk 3-6, 6-2, 6-4 with six breaks over the last two sets and No. 5-seed Elena Vesnina controlled the third set for a 7-6 (8-6), 6-7 (5-7), 6-1 win over Vania King.
Local wild-card entrant Nicha Lertpitaksinchai was a 6-3, 6-3 winner over Aleksandra Krunic. It was the first WTA main draw win for Lertpitaksinchai.
Also Tuesday, qualifier Alexandra Dulgheru defeated Yulia Putintseva 6-1, 6-7 (6-8), 6-4, Vera Zvonareva took out Peangtarn Plipuech 6-3, 6-2 and Tadeja Majeric beat Hsieh Su-Wei 6-2, 7-6 (7-4).