Petra Kvitova left fellow Czech left-hander Lucie Safarova staring at possible elimination from the WTA Finals when she beat her 7-5, 7-5 on Wednesday.
Two-time Wimbledon champion and world number five Kvitova, 25, has now dominated her friend and compatriot 8-0 on hardcourts, grass and clay.
“I’m really glad that I was able to play and win the kind of match after my loss in the first match here,” said Kvitova, who fell to Germany’s Angelique Kerber in straight sets on Monday.
Safarova is now relying on Garbine Muguruza beating Kerber in Wednesday’s later White Group match to stay alive in the eight-player season finale.
The world number nine looked set to force a decider after racing to a 3-0 lead in the second set, but she squandered her lead with weak serving.
“For sure it was a difficult match. I know that Lucie wasn’t really healthy weeks ago and I’m just happy that she’s here as well,” Kvitova said.
“It’s great to have two Czechs in the WTA Finals.”
The victory was vital for Kvitova, who would also have been facing potential elimination if she had lost her second match in the White Group round robin.