Results from the WTA clay-court tournament in Stuttgart on Thursday (x denotes seeding): 2nd rd Karolina Pliskova (CZE x6) bt Jelena Ostapenko (LAT) 6-7 (7/9), 6-4, 6-3 Aryna Sabalenka (BLR x5) bt Anna-Lena Friedsam (GER) 6-4, 6-2 Simona Halep (ROU x2) bt Marketa Vondrousova (CZE) 6-1, 6-3 afp