SHENZHEN, China - Entering the final day of Red Group round-robin play at the Shiseido WTA Finals Shenzhen, No.1 seed Ashleigh Barty knew that only a win would guarantee her progress into the weekend's semifinals - and accordingly posted one with maximum efficiency, defeating No.6 seed Petra Kvitova 6-4, 6-2 in one hour and 29 minutes.

As recently as January, Barty had fallen to a 0-4 career record against the Czech after two heartbreaking losses on her home turf, in the Sydney final and Australian Open quarterfinals. But since then, she has bounced back in style to pull the rivalry back: today marks the 23-year-old's third consecutive win over Kvitova, following her victories in the Miami and Beijing quarterfinals, and her first in straight sets. The result also ensures Barty's position at the top of the Red Group this week, with Belinda Bencic and Kiki Bertens squaring off for second place in today's second match.

Barty has never seen her record against Kvitova as cause for concern, though. Indeed, as she said afterwards: "I think playing against Petra is probably one of my favorite things to do, if I'm being honest. Win or lose, it's going to be a great match. It's going to be played in the right spirit. I just enjoy the challenge of playing against Petra. She really does bring out the best in me.

"It's a challenge that I love. It's a challenge that I thrive on. I think each time I've played Petra, I've become a better player having learned what's happened during that match."

Today, the most satisfying aspect of that challenge was how Barty dealt with the formidable Kvitova serve: "I was particularly happy with the way I was able to return tonight," she assessed. "I think Petra changed her serving spots to her usual kind of serving spots. I think she was trying to take a little bit more of a risk. That kind of worked in my favor a bit. Really happy with how we were able to nudge in front early in both sets and keep the foot down."

Over the course of a tight first set, Barty's cool play in big moments - particularly on serve - came to the fore repeatedly in order for her to edge the opening act. The Australian was the first to pressure her opponent's serve, holding two break points in the third game - and although she was unable to take them that time, she didn't let up, with two excellent passes sealing the breakthrough two games later.

That was a tactic that also had the effect of halting Kvitova's initial strategy of rushing the net at every opportunity. For the remainder of the set, the Sydney and Stuttgart champion backed off somewhat - and in contrast to Barty, despite some highlights-reel magic on the forehand and dropshot in particular, seemed unable to conjure it up on points that mattered.

Having dropped serve, Kvitova would hold four break points over the course of eight deuces in Barty's next two service games - benefiting from the good fortune of two dead net cords in the first - but was unable to take any of her chances. Any opening would be slammed shut either by Barty coming up with a clutch serve, or by Kvitova herself committing one of her 20 unforced errors in the set - and accordingly it was the Roland Garros champion who maintained her lead to close out the set to 15.

The second set again opened with Kvitova shooting herself in the foot: from 30-0 up, the 29-year-old netted two dropshot attempts and coughed up her fourth double fault to open the door for Barty. The World No.1 needed little encouragement to rise to the occasion with some magic of her own, closing out the break with a beautifully lofted lob and some elegant forecourt play.

This set the tone for a one-sided set: again, Kvitova had opportunities on the Barty serve, stretching her opponent to two deuces in the second game and holding a 0-30 lead in the fourth; and again, the two-time Wimbledon champion was unable to find her best tennis when it came to closing out games. Instead, it was Kvitova who would concede her serve for a second time, again from game point up, thanks to another assortment of double faults and unforced errors - before having to watch Barty extricate herself from danger to build a 4-0 lead with back-to-back aces.

This lead would prove unassailable: maintaining a first serve percentage of 62% compared to her opponent's 50%, Barty would not face a break point during the whole of the second set. Though, in what is becoming a Kvitova trademark, the former World No.2 was able to blitz two spectacular forehands to save two match points, it was too little, too late her 21 winners for the day had been outweighed by 31 unforced errors, compared to Barty's positive ratio of 23 winners to 18 unforced errors, and a service winner on Barty's third match point would seal victory emphatically.