Singapore - Karolina Pliskova issued a warning to her opponents at the WTA Finals with a convincing straight-sets victory against defending champion Caroline Wozniacki.
The dynamic 26-year-old's easy 6-2, 6-4 triumph in Singapore was sweet revenge for Pliskova, who lost to Wozniacki in the semis at last year's WTA Finals.
Pliskova had strapping on her lower right leg but moved well against the sluggish second seed.
The hard-hitting Czech was not broken on serve for the entire match and fittingly closed it out with an ace.
"I felt good from the baseline and it was not all about my serve," Pliskova said after the match.
"She started a bit nervous in the beginning, it's always tough to defend a title."
The world No 8 stunned Wozniacki with a brilliant first set highlighted by trademark booming ground strokes.
She saved two break points in her opening service game before overwhelming the Australian Open champion en route to winning five straight games.
Wozniacki, who had only played two top-10 players this year before Sunday, struggled with rhythm in the first set and made several uncharacteristic errors.
The one-way traffic continued in the second set with Pliskova breaking immediately, saving three break points in the next game to the frustration of her opponent.
The Dane started to find her groove but squandered break points in the eighth and 10th games in a disappointing start to her title defence.
Earlier, a determined Svitolina ended her long-time jinx against former Wimbledon champ Kvitova, cruising to a straight sets win.
The world number six triumphed 6-3, 6-3 in just 89 minutes in the tournament opener, easily overcoming a lacklustre Kvitova, who had 29 unforced errors and seven double faults.
Svitolina had won just one set in seven straight harrowing defeats to the Czech but impressively turned the tables.
"Winning this match definitely gives me lots of confidence," Svitolina told reporters after the match.
"I played good, quite solid from the baseline and putting pressure on Petra. I was really, really solid, and I think this was really the key."
Kvitova rued her subpar opening performance.
"Wasn't the best start, but the good thing is there is still a chance to play better and to improve and maybe go somewhere forward," she said.
Kvitova's trademark firepower moved Svitolina around the hard court but the Ukrainian's defence was up to the task.
A composed Svitolina made just four unforced errors in the opening set in a notable contrast to her error-riddled opponent, who struggled badly on serve and conceded the first set after her fifth double-fault.
Svitolina broke in the sixth game and held her nerve to claim just her second victory against Kvitova from nine meetings.
The Red Group action starts on Monday with number one seed Angelique Kerber playing Kiki Bertens and Naomi Osaka squaring off against Sloane Stephens in a battle of the past two US Open champions.
Results from the WTA Finals tennis in Singapore on Sunday (x denotes seeding):
Elina Svitolina (UKR x6) bt Petra Kvitova (CZE x4) 6-3, 6-3
Karolina Pliskova (CZE x7) bt Caroline Wozniacki (DEN x2) 6-2, 6-4