Wimbledon champion Elena Rybakina came from a set down to defeat Madison Keys 5-7, 6-3, 6-3 in the first round of the Agel Open on Monday.
Rybakina had lost to Keys this year at the French Open and Cincinnati.
In other first-round matches in the eastern Czech city of Ostrava, Ajla Tomljanovic of Australia defeated Zhang Shuai of China 6-3, 6-3, and local hope Petra Kvitova overcame American Bernanda Pera 6-3, 2-6, 6-4.
Fresh from her second title of the year in Seoul last month, Ekaterina Alexandrova of Russia knocked out former No. 1 Victoria Azarenka of Belarus 6-4, 4-6, 6-2.