Charleston: Donna Vekic of Croatia upset Britain's Heather Watson 6-3, 4-6, 7-5 in the opening round of the Family Circle Cup on Monday.
The 18-year-old Vekic raced out to a 6-3, 4-2 lead before Watson, the 16th seed, took seven of the next eight games to capture the second set and take a 3-1 lead in the second.
Vekic responded by leveling the score at 5-all before breaking Watson at love to win the match.
In other matches, Czech qualifier Lucie Hradecka of the Czech Republic defeated 11th-seeded Zarina Diyas of Kazakhstan, 4-6, 6-1, 6-3, Mona Barthel of Germany beat Timea Babos of Hungary, 6-3, 6-3, and Kristina Kucova of Slovakia topped Croatia's Mirjana Lucic-Baroni 6-3, 3-6, 6-3.
Canada's Eugenie Bouchard is the top seed and received a first-round bye.