Round-robin doubles action at the WTA Finals Riyadh presented by PIF started with two Green Group upsets on Saturday, each from a set down.

Last year's WTA Finals runners-up Nicole Melichar-Martinez and Ellen Perez, the No.6 seeds, opened this year's edition by bouncing back from a one-sided first set and defeating No.3 seeds Hsieh Su-wei and Elise Mertens, 1-6, 6-1, [10-6]. 

WTA Finals Riyadh: Scores | Schedule | Standings

The first two sets in the opening Green Group match were completed in less than an hour, as both winning teams sprinted out to 4-0 leads. That set the stage for a tense match tiebreak, where the American-Aussie pair won five of the last six points to wrap up the 70-minute victory.

"I thought it was super important just to compete," Perez said post-match. "Everyone can play good tennis here, and it's just finding ways to win, getting balls in the court and competing. I think we did a good job of that to be able to fight back."

It reversed the result of the only match between the two teams in 2024: a 6-2, 7-6(5) victory for Hsieh and Mertens at Indian Wells, where they won the title.

"Elise, I think she only missed one ball in the first set," Melichar-Martinez said. "We just tried to regroup, and tell each other, 'This is working, this is working,' even though it wasn't really working that much, just try and get a few more balls in the court, and hopefully they miss some."

Melichar-Martinez and Perez ended the match with 17 winners to 16 unforced errors, with Hsieh and Mertens hitting just 10 winners to 16 unforced errors.

Then, in the late match, No.8 seeds Katerina Siniakova and Taylor Townsend won a clash between two of this year's Grand Slam-winning teams.

Reigning Wimbledon champions Siniakova and Townsend saved a match point and edged past No.1 seeds and reigning US Open champions Lyudmyla Kichenok and Jelena Ostapenko 3-6, 6-3, [11-9].

"Definitely we were trying to be aggressive, and be really everywhere at the net," Siniakova said in their on-court interview. "I think we really did a great job staying in the match, playing every point, because with no-ad scoring, super-tiebreak, you never know. We did a really good fight, and I’m just proud."

Kichenok and Ostapenko were the dominant team to start, leading by a set and a break at 6-3, 1-0. But Siniakova and Townsend broke the top seeds' serves twice in succession to stem the tide, eventually clinching the second set and setting up the match-tiebreak.

Siniakova/Townsend save match point, upend No.1 seeds at WTA Finals

The closely-contested match-tiebreak saw Kichenok slam an overhead winner to reach match point at 9-8, but she misfired long on a backhand and the teams switched sides again at 9-9.

A powerful Siniakova overhead gave her team their first match point at 10-9, and she and Townsend sealed victory when Kichenok found the net at the end of a tense rally.

Each squad broke serve three times and it came down to the narrowest of margins in the breaker. In the end, the victors were 2021 WTA Finals doubles champion Siniakova, who is playing her sixth WTA Finals, and Townsend, who is contesting her first.

"It means a lot for this to be my first [WTA Finals] in my career," Townsend said. "I’ve been on tour for 11 years, so it’s really a huge accomplishment for me to be able to have a child and come back and be on this stage."