SINGAPORE — Defending champion Caroline Wozniacki earned her first victory at this year's WTA Finals, beating Petra Kvitova 7-5, 3-6, 6-2 on Tuesday.

Elina Svitolina earned her second straight win in the other group match, outlasting Karolina Pliskova 6-3, 2-6, 6-3. The results mean all four players are still in contention to advance to the semifinals from the White Group.

Wozniacki, who became the first Danish woman to win a Grand Slam title at this year's Australian Open, is now 1-1, while Kvitova is 0-2.

"I played much better today," Wozniacki said on court after the match. "I returned well. I served well. Against Petra, she's so powerful, you have to stay on your game. I just tried to stay focused and get a lot of balls back.

"I always believe in myself and when I'm out on the court I believe I'm going to win." Kvitova, who won the WTA Finals title in her debut appearance at the year-end tournament in 2011, was the one taking chances on Tuesday. But Wozniacki played steadier defense and waited for the Czech to make mistakes.

Kvitova finished the match with 40 winners and 40 unforced errors. Wozniacki had 19 winners and 14 unforced errors.

Wozniacki, who broke her opponent in the first and fifth games of the deciding set, took a medical timeout to have her left knee bandaged when Kvitova was leading 3-1 in the second.

Svitolina failed to serve out the match at 5-2 in the third set but converted her third match point in the next game with a forehand winner.

The most tense moment of the match came in the third game of the first set, which lasted 15 minutes and went to deuce 10 times. Svitolina finally held after saving six break points.

"Actually, I was thinking how long we are playing this game? No more," Svitolina said, smiling. "We were both I think a little bit struggling with our nerves." Svitolina only needs to win a set in her last round-robin match against Wozniacki to reach the semifinals.