SHENZHEN, China - No.1 seeds Timea Babos and Kristina Mladenovic pulled off two remarkable comebacks to edge out No.7 seeds Samantha Stosur and Zhang Shuai 1-6, 6-4, [10-8] in the semifinals of the Shiseido WTA Finals Shenzhen.

The defending champions were dominated from the outset and trailed 1-6, 0-2, as well as 3-7 in the match tiebreak, but showed immense fighting spirit to overturn both deficits, extending their winning streak at the year-end finale to seven together and 10 for Babos, who was also the 2017 champion alongside Andrea Sestini Hlavackova.

Today, Stosur got off to a nervous start, dropping serve with a series of errors and a double fault. That wouldn't last long, though, as the Australian-Chinese duo roared back with a spell of majestic form to reel off eight consecutive games.

Both would display superb reflexes and creative shotmaking: Stosur came up with a half-volleyed forehand pass from the baseline to hold for 4-1 and sealed the final two games of the set with excellent volleying, while almost everything Zhang touched turned to gold. On big points, the Australian Open champions were even better. Capturing a run of three consecutive deciding points meant that they emerged from the relatively tight initial passage of play with a hefty 4-1 lead, and another would consolidate an opening break of the Babos serve in the second set as Zhang held for 2-0.

The defending champions were not about to exit the tournament tamely, though. Babos and Mladenovic had both been loose with their errors both off the ground and at net in the first set, but the Frenchwoman in particular picked up her form to claw back into the contest. A firm drive volley from Mladenovic snapped their losing streak of games, and thereafter her smash and backhand return would prove formidable weapons in breaking the Stosur serve and setting the stage for a gripping second set.

With both teams now playing well, opportunities were rare - but having posted a series of impressive holds to build a 5-4 lead, the Franco-Hungarian team struck on, unexpectedly, the Zhang serve. The Chinese player had still seemed to be in her purple patch as she thundered a backhand winner for a 30-0 lead, but a double fault opened the door - and, swarming the net, Babos and Mladenovic stormed through it, taking their second set point as a Stosur volley found the net.

A riveting match tiebreak saw momentum oscillate wildly throughout. Babos and Mladenovic got out to a lead first, moving up 3-1 thanks to powerful play from Babos and yet another Mladenovic backhand return nailed down the line - only to drop six comsecutive points in a cascade of tight errors.

Leading 7-3, though, Stosur and Zhang couldn't quite put their opponents away. Two remarkable gets - one lob from Babos and a backhand from Mladenovic - helped the Roland Garros champions steal two key points they had been almost out of, and the Babos backhand lit up again as they reeled off seven of the last eight points to set up a final date against either No.2 seeds Hsieh Su-Wei and Barbora Strycova or No.8 seeds Anna-Lena Groenefeld and Demi Schuurs.