Australian Open finalist Petra Kvitova has won eight straight games to take control of the match before needing a tiebreaker to finally beat Victoria Azarenka 6-2 7-6 (7-3) in the second round of the St. Petersburg Ladies Trophy.
The Czech ace, playing her opening match on Wednesday after a first-round bye, went from trailing 2-1 in the first set to a 3-0 lead in the second.
But she double-faulted on match point at 5-1 to let Azarenka back into the match.
Kvitova will next face either eighth seed Donna Vekic or lucky loser Veronika Kudermetova in the quarter-finals.
Maria Sharapova withdrew from the tournament with a right shoulder injury, hours before she was to play Daria Kasatkina in the second round.