Klara Zakopalova came from behind to beat fellow Czech Lucie Safarova 5-7 6-3 6-1 in the first round of the Rogers Cup in Toronto.
Safarova, four times a winner on the WTA circuit, gained a decisive early break on her way to taking the first set against her experienced compatriot.
Thirty-one-year-old Zakopalova regained parity in the match by winning the second and went on to secure victory with a dominant performance in the deciding set.
Zakopalova will face fifth-seed Sara Errani in the second round.