BEIJING, China - The doubles Porsche Race to Singapore is heating up at the China Open, with teams on the qualification bubble fighting for the final four spots in Beijing.

The BNP Paribas WTA Finals Singapore presented by SC Global field for doubles is halfway complete, with four teams already qualified for the season-ending event: Barbora Krejcikova and Katerina Siniakova hold the top spot, followed by Kristina Mladenovic and Timea Babos at No.2. And based on their results in Wuhan, Andrea Sestini Hlavackova and Barbora Strycova qualified at No.3 and Demi Schuurs and Elise Mertens at No.4.

Read more: Porsche Race to Singapore Update, October 1: Sabalenka adds suspense to final weeks 

In Beijing with four spots up for grabs, a pair of teams in the Top 8 took a big step forward in their qualification effort.

No.6 seeds Andreja Klepac and Maria Jose Martinez Sanchez - who sit at No.6 on the Porsche Race to Singapore - came back from a set down to defeat Raquel Atawo and Anna-Lena Groenefeld 6-7(5), 7-5, 10-7 and book their spot in the China Open quarterfinals. The unseeded duo of Atawo and Groenefeld were likely hoping for a deep run in Beijing to bolster their qualification chances - they occupy the No.10 spot on the Race to Singapore.

Klepac and Martinez Sanchez will take on the No.2 seeds Sestini Hlavackova and Strycova in the next round. The already-qualified Czechs also had a hard battle to reach the quarterfinals, coming back from a set down to defeat Aleksandra Krunic and Katerina Siniakova 2-6, 7-6(3), 10-4.

Kveta Peschke and Nicole Melichar also took a big step toward Singapore today. The No.5 seeds, who are in the No.8 spot on the Race to Singapore leaderboard, eased past Lara Arruabarrena and Darija Jurak 6-3, 6-2 to reach the Beijing quarterfinals.

They’ll take on last week’s Wuhan champions, the No.4 seeds Elise Mertens and Demi Schuurs in their next match. Mertens and Schuurs have already qualified for Singapore based on their Wuhan run, and today they defeated Anastasia Pavlyuchenkova and Anastasija Sevastova in straight sets, 7-5, 6-2.