SHENZHEN, China -- Tuesday turned out to be a successful day for this season’s Grand Slam-winning doubles teams at the Shiseido WTA Finals Shenzhen.

2019 Australian Open champions Samantha Stosur and Zhang Shuai kicked off the second day of round-robin play in the Purple Group with a 4-6, 6-4, [10-5] comeback victory over Wimbledon runners-up Gabriela Dabrowski and Xu Yifan.

Later, 2019 Wimbledon champions Hsieh Su-wei and Barbora Strycova also needed a match tiebreak to move into the winner’s circle, outlasting Barbora Krejcikova and Katerina Siniakova, 6-2, 1-6, [10-5], completing their victory just after midnight.

After two matches for each team in the Purple Group, No.2 seeds Hsieh and Strycova are currently atop the group with a 2-0 record, which has clinched them a berth in the semifinals. Stosur/Zhang and Krejcikova/Siniakova will face each other on Thursday for the second semifinal spot coming out of their group.

"It was a really tough match for us, but we played really good," said WTA Doubles World No.1 Strycova, after her team's late-night victory. "We helped each other, and at the end, we were maybe -- I would not say lucky, but we played a better tiebreak."

Hsieh and Strycova seemed to have everything going their way after the first set of their encounter with the all-Czech duo. Strycova garnered the first break of the match with a volley winner, putting her team up 3-1, and she and Hsieh cruised to the one-set lead from there. Hsieh and Strycova fired ten winners and just two unforced errors in the opening frame.

However, Krejcikova and Siniakova, winners of two Grand Slam titles in 2018, picked up their first service break of the tilt in the opening game of the second set, and they completely turned around the momentum from there. They raced through the second stanza, claiming it 6-1 after Krejcikova fired a forehand winner down the line on set point.

Strycova, though, started the match tiebreak on fire, charging the net to put away three smashes in a row and grab the early 3-1 lead. She and Hsieh continued to hold their lead, with Hsieh firing an error-forcing forehand to put her squad ahead 8-5.

With the match on Hsieh’s racquet, another Strycova putaway gave their pairing four match points, and they converted their first opportunity after a long Krejcikova return. Each team finished the clash with 18 winners, but Hsieh and Strycova had four fewer unforced errors overall, leading to their narrow 75-minute victory.

"It was our goal to qualify here," said Strycova. "We are here and try to enjoy every moment. We have a big team, so we enjoy on and off the court as well. It’s great to be here and we are really appreciative."

Earlier, in the first match of the day, Stosur and Zhang eked out their 86-minute victory with 21 winners to their opponents' 19, fighting back from their first round-robin loss to Hsieh and Strycova on Sunday.

"We didn’t practice yesterday, I think that’s the big key for us!" Zhang said, with a laugh. "We ate good, slept well, we tried to relax."

"We definitely stayed positive," Stosur added to her teammate's comment. "The other match [against Hsieh/Strycova], we played very well."

In the opening frame, though, Dabrowski and Xu fought back from an 0-3 deficit, winning five games in a row with solid play in the forecourt. Dabrowski fended off three break points on her serve to close out the first set, which ended with a Xu putaway.

Stosur was imperiled on her serve early in the second set, as Dabrowski and Xu held four break points at 1-1 which would have given them a commanding set-and-a-break lead. But Stosur methodically erased them all, and she and Zhang staved off five more break points in the set en route to 5-4. There, aggressive play by the Australian-Chinese duo led to a love break, with Stosur polishing off the set with a winning volley.

The groundstrokes of Zhang pulled her team to an early 3-1 lead in the match tiebreak, while Stosur's volleys extended their lead further to 7-2. They reached quintuple match point at 9-4, and though Xu saved one match point with a strong serve, Stosur fired a backhand return winner on the second opportunity to seal victory.

"I think both of the teams, we probably won the sets we shouldn’t have won!" Stosur laughed. "We got off to a really good start, 3-0, then let that kind of slip away with some unforced errors, and we really let them back into the match. The second set, they had a lot more opportunities to break us early on, but we held in there, and did what we could to try and keep holding serve, and then we got our opportunity and we took it."

"In the super-tiebreak, we just came out more aggressive," Stosur continued. "We were very clear and focused on what we wanted to do, and thankfully we executed that very well."