MELBOURNE, Australia - No.5 seeds Timea Babos and Rohan Bopanna ended the title defence of unseeded Abigail Spears and Juan Sebastián Cabal in a tight 6-4, 7-6(5) contest, coming from a break down in both sets to move into the mixed doubles quarterfinals.

It was a successful day on double doubles duty for Babos in particular, who had earlier reached the women's doubles final alongside Kristina Mladenovic with a 6-4, 6-2 win over Hsieh Su-Wei and Peng Shuai.

Despite this being just their first tournament together, the Hungarian-Indian duo had not dropped a set through two rounds - and though a neat Cabal volley captured the Babos serve in the third game, the seeded pair's form held.

Aggressive returning from Babos pulled them into contention on the Colombian's next service game - and a double fault promptly handed the lead back.

With Bopanna's serve impregnable - the 37-year-old dropped just three points behind it in the first set - the Cabal delivery was again the target in the ninth game. An ill-timed flurry of missed Spears volleys and overheads put Babos and Bopanna a set up on their fourth set point.

Unexpectedly, the second set began with a Bopanna wobble on serve, as the 2017 Roland Garros mixed doubles champion lost his serve with a handful of loose errors. This time, the American-Colombian duo managed to consolidate their lead, with Spears fending off three break points to pull ahead to 3-1.

Once more, it was the Cabal serve that proved vulnerable, though. Upping the ante on return again, Babos's power was able to put her opponents on defence, setting Bopanna up for efficient finishing blows.

Babos and Bopanna would also prove far more efficient on deciding points than the defending champions, winning six of the match's eight sudden-death points - including two breaks of the Cabal delivery (for 3-3 and 5-5, preventing the 31-year-old from serving out the second set), and a key Babos hold to take the set into a tiebreak.

There, despite wobbles on serve from both sides (consecutive double faults from Babos were followed two points later by one from Spears), Babos and Bopanna's aggression continued to pay off as they set up a quarterfinal against either unseeded María José Martínez Sánchez and Marcelo Demoliner or wildcard pair Storm Sanders and Marc Polmans.