Wozniacki battles through knee complaint to down Kvitova

Despite struggling with a knee injury, Caroline Wozniacki boosted her chances of reaching the WTA Finals last four by beating Petra Kvitova.

Caroline Wozniacki celebrates against Petra Kvitova

Caroline Wozniacki battled through a troublesome knee complaint to earn a crucial three-set victory over Petra Kvitova in the White Group of the WTA Finals.

Defending champion Wozniacki and Kvitova lost their opening matches of the round-robin phase to crank up the importance of Tuesday's contest in Singapore.

It was Wozniacki who struck first in a tense opening set, but a problem with her left knee limited the Dane's movement and allowed Kvitova to level the match.

The see-saw nature of the match went back in Wozniacki's favour, though, and the second seed completed a 7-5 3-6 6-2 victory to end a four-match losing streak over Kvitova dating back to 2014.

Victory reignites Wozniacki's bid to reach the semifinals, while Kvitova - who mixed 40 winners with as many unforced errors - stayed afloat after Karolina Pliskova's loss to Elina Svitolina.

It took until game eight for the first break of the match when Wozniacki followed up a fierce backhand with a thumping forehand winner.

The Dane failed to serve out the opener, wasting a set point in the process, as Kvitova hit back immediately and then earned another break-point chance in game 11.

That danger was quelled and, with Kvitova serving to stay in the set, Wozniacki saw another set point go missing before the third time proved a charm when the Czech put a forehand into the net.

After a break apiece to start the second, Kvitova stole in front again in game three when she correctly reviewed a ball called out and Wozniacki needed strapping on her knee during a medical timeout after game four.

A glorious deft lob briefly levelled the set at 3-3, but Kvitova quickly regained the advantage and, with Wozniacki's movement now clearly hindered, she cantered through the remaining games.

But Wozniacki gained a second wind as the momentum swung once again.

Wozniacki broke at the first time of asking with a double-backhand pass at the end of a majestic rally and, with Kvitova – who is asthmatic – visibly struggling with her breathing at a change of ends, a break of love followed to establish a 4-1 lead.

From there it was a formality for Wozniacki, who can now look ahead to her final group match with Elina Svitolina.