SINGAPORE -- Elina Svitolina of Ukraine beat Petra Kvitova 6-3, 6-3 in the first match of the WTA Finals on Sunday to snap a seven-match losing streak against the Czech player.

The seventh-ranked Svitolina, making her second consecutive appearance in Singapore, only earned qualification to this year's tournament last week when Dutchwoman Kiki Bertens failed to reach the Moscow semifinals. Later, Bertens made the final eight when No. 1-ranked Simona Halep withdrew with a herniated disk in her back.

"It's very nice to be back in Singapore and I'm very, very happy with the match tonight, with the performance tonight," Svitolina told the crowd. "I had to stay focused and be strong mentally. I had to play quickly and keep moving my feet so I need a massage now.

"You have to play your best level because everybody is very strong playing here."

Svitolina, who now holds a 1-0 record in the White Group, had only beaten Kvitova once before in their first match at the 2014 Cincinnati tournament. Sunday's victory was Svitolina's first against a top-10 opponent since May.

The Ukrainian player briefly left the post-match press conference but later returned.

"I'm just not feeling good," said Svitolina after returning. "I was really, really solid, and I think this was really the key."

The fifth-ranked Kvitova, who won the year-end title in 2011, never looked settled and struggled with her serve throughout the 1 hour, 29 minutes match. Her first serve percentage was a meagre 55, which made the task of beating Svitolina near impossible.

She double-faulted seven times in the match, including on set point in the first for Svitolina. Six of her seven double faults came in the first set.

"I think she really played very consistent," Kvitova said. "Overall, yeah, it wasn't the best start, but the good thing is that there is still a chance to play better and to improve, and maybe go somewhere forward."

The Czech surrendered her serve in the opening game of the match but managed to recoup the break in the next game. But she surrendered her serve two additional times in the first set to fall behind.

Svitolina set up the second set win by breaking Kvitova's serve to go ahead 4-2.

Kvitova came into Singapore with a tour-leading five titles this season.

Defending champion Caroline Wozniacki takes on Karolina Pliskova in the second match later Sunday.