Luxembourg - Top-seeded Caroline Wozniacki of Denmark struggled to a 6-3, 7-6 (2) win over local favourite Mandy Minella to reach the second round of the Luxembourg Open on Tuesday.
Second-seeded Sloane Stephens of the United States made lighter work of her day as she beat 2009 champion and Swiss wild card Timea Bacsinszky 6-3, 6-3.
Two seeds fell: No 4 Kirsten Flipkens of Belgium lost to Katarzyna Piter of Poland 6-4, 6-2, and No 6 Mona Barthel of Germany lost to Stefanie Voegele of Switzerland 1-6, 6-4, 7-6 (3).
Third-seeded Sabine Lisicki of Germany also was in trouble early on against Croatia's Donna Vekic before she recovered to win in three sets 2-6, 6-3, 6-0.
Results from first day of the WTA Luxembourg Open on Tuesday (x denotes seeding):
Sabine Lisicki (GER x3) bt Donna Vekic (CRO) 2-6, 6-3, 6-0
Caroline Wozniacki (DEN x1) bt Mandy Minella (LUX) 6-3, 7-6 (7/2)
Yvonne Meusburger (AUT) bt Irina Begu (ROM) 6-4, 6-2
Su-Wei Hsieh (TPE) bt Kristina Kucova (SVK) 4-6, 7-6 (7/2), 6-3
Katarzyna Piter (POL) bt Kirsten Flipkens (BEL x4) 6-4, 6-2
Stefanie Vogele (SUI) bt Mona Barthel (GER x6) 1-6, 6-4, 7-6 (7/3)
Karolna Pliskova (CZE) bt Lourdes Dominguez (ESP) 5-7, 7-5, 6-1
Sloane Stephens (USA x2) bt Timea Bacsinszky (SUI) 6-3, 6-3