SINGAPORE — Caroline Wozniacki overcame a mid-match wobble and withstood a barrage of big hitting to get her WTA Finals title defence back on track with a 7-5, 3-6, 6-2 victory over Petra Kvitova at the Singapore Indoor Stadium Tuesday.

In the second White Group encounter of the day, Elina Svitolina moved to the brink of the semifinals with a gutsy 6-3, 2-6, 6-3 win over Karolina Pliskova, the Ukrainian recording her second straight win of the tournament to top the pool.

Wozniacki and Kvitova came into their contest on the back of opening defeats in round robin play but the Danish world number three ended a run of four straight losses to the Czech to stay alive in the eight-woman tournament for at least one more match.

The Dane, who started her campaign with a 6-2, 6-4 loss to Pliskova on Sunday, spent most of the match against Kvitova pinned on the baseline but her consistency and patience proved vital as she pulled away in the final set.

"I played much better today. I served and returned pretty well, and moved really well against a player who is so powerful that you have to stay on your game," Wozniacki said

"You never know what is going to happen against Petra, so I just stayed focused and got a lot of balls back."

The match was a cagey affair from the outset with seven holds of serve in a row. But after they traded breaks as the intensity levels picked up, Wozniacki broke again to seal the opener when Kvitova blasted a forehand into the net.

Kvitova took control of the second set with an early break, then lost momentum when Wozniacki took a timeout for treatment on her knee, before regaining the upper hand to level the match with a sliced backhand winner on her third set point.

Sensing her title defense was hanging by a thread, Wozniacki regrouped to break at the start of the decider when she put away a backhand to win the longest rally of the match, and ran away with the contest as Kvitova wilted.

The 28-year-old Wozniacki sealed victory on her first match point with a big serve that Kvitova sent long, and will hope to complete round robin play with a victory over Svitolina to secure a semifinal berth.

Svitolina was a bundle of energy at the start of the second match, full of intensity and covering every inch of the court as she rode her early momentum to wrap up the opening set with a forehand winner that was greeted with a big clenched fist.

The Ukrainian had played almost perfect tennis until midway through the second set when a combination of good fortune and rasping cross-court winners earned Pliskova her first break of the tie, a feat she repeated two games later to level the match.

Svitolina shrugged off the setback to come storming out of the blocks in the decider, racing to a 4-0 lead that she carried all the way to victory despite a late fightback from Pliskova.

She only needs to take a set off Wozniacki on Thursday to reach the last four for the first time but as it stands, all four players can still mathematically reach the semifinals.

Cilic downs Shapovalov

Third seed Marin Cilic eased into the second round of the Swiss Indoors tournament with a 6-4, 6-2 victory over young Canadian Denis Shapovalov in Basel Monday.

The Croatian, who was champion in Basel in 2016 and can seal a spot at the ATP Finals if he wins the title again this year, opened up a 4-0 lead in the first set before 19-year-old Shapovalov got on the scoreboard.

The Canadian wilted further in the second set, however, and his cause was not helped by his 23 unforced errors as Cilic wrapped up a routine victory in one hour and 15 minutes.

Next up for Cilic is Romanian qualifier Marius Copil, who beat American Ryan Harrison 6-2, 7-6(8).

Taylor Fritz also cruised into the second round with a 6-0, 7-5 win over Serbia’s Laslo Djere and the American will face Swiss wild card Henri Laaksonen next.

A back injury suffered during a Sunday practice session with compatriot Roger Federer forced Stan Wawrinka to pull out of the tournament.

“I turned my back, and retiring was the only decision I could make,” said the three-time Grand Slam champion, adding that he will end his season early and not play at the Paris Masters next week.

The withdrawal of Wawrinka, ranked 68th in the world as he continues to fight to fully recover more than a year after two knee surgeries, comes after Federer made an injury confession of his own.

Federer revealed in the run-up to the start at the St Jakobshalle that he had been suffering since the summer with a hand injury, which the 20-time Grand Slam winner insisted was fine now.

Federer, the holder, is seeking a ninth title at the event where he got his start in the sport as a teenage ballboy. Wawrinka has been playing in fits and starts this season, losing in the Shanghai first round this month after reaching the semifinals in September in St Petersburg.

Wawrinka, twice a semifinalist in Basel, was to have faced Adrian Mannarino in the first round Wednesday. — Agencies