Serbia’s Novak Djokovic has beaten Spain’s Rafael Nadal to ensure the ATP Cup goes down to the final doubles match.

Djokovic beat the world No.1 in 6-2 7-6 in Sydney after Nadal’s teammate Roberto Bautista Agut had a straight-sets victory over Dusan Lajovic earlier in the night.

The world No.10 had too much firepower for Lajovic, chalking up a 7-5 6-1 victory to finish with a perfect six-from-six record for the competition – without dropping a set.

Nadal now has a nine-match, seven-year hardcourt losing streak to Djokovic.

Barty loses doubles, Williams wins in Auckland

Ashleigh Barty and Kiki Bertens have fallen short in the Brisbane International doubles final, with the world No.1 missing a match point to lose to top seeds Hsieh Su-wei and Barbora Strycova.

On the final day of a tournament that some players felt had been overlooked because of the success of the ATP Cup, Karolina Pliskova beat American Madison Keys in the singles final.

The Czech world No.2 on Sunday became the first player to win the event three times, Pliskova again serving without fear in a 6-4 4-6 7-5 tussle.

In New Zealand, Serena Williams also showed she’s on track for a big summer, winning the Auckland Classic and marking her first tournament victory since returning from a maternity break.

Williams beat compatriot Jessica Pegula 6-3 6-4 in one hour and 35 minutes, saying afterwards she had “been waiting two years for this moment”.

Serena Williams with daughter Alexis after winning the Auckland Classic. Photo: AAP

“It feels good. It’s been a long time. You can see the relief on my face,” Williams said.

Meanwhile Karolina Pliskova will treat herself to one day after the world No.2 claimed a historic third Brisbane International trophy.

The clean-hitting Czech took just over two hours to beat Madison Keys 6-4 4-6 7-5 on Sunday, outlasting the valiant American despite a near three-hour semi-final tussle against Naomi Osaka on Saturday night.

It was Pliskova’s third Brisbane title in four years, having made the semi-finals in 2018 between wins in 2017 and 2019.

And it’s the first time she’s defended a trophy in a career that’s now netted 16 titles.

Karolina Pliskova celebrates her win at the Brisbane International. Photo: AAP

Earlier, Barty reminded home fans of her doubles pedigree as the unseeded pair got within a point of the title in the second-set tiebreaker.

But the world No.1’s clutch serving and deft hands weren’t enough as the Wimbledon champions prevailed 3-6 7-6 (9-7) 10-8 on Pat Rafter Arena.

“A couple points here and there … that’s the beauty and the beast in this kind of format .. it’s kind of on a knife’s edge, it can change really quickly,” Barty said.

Barty had lost her second-round singles match to qualifier Jennifer Brady – her first match of the year after a first-round bye.

Her doubles run meant the Queenslander still earned about $65,000 at the tournament despite her early singles exit, all of which she pledged to donate to the Red Cross Fire Appeal.

With everything that’s been going on in Australia, the way that everyone’s come together’s been incredible and all and all I’m bloody proud to be an Aussie.”

All four players in the doubles final will compete in the Adelaide International singles draw, where Barty is top seed in her final hit-out before the Australian Open from January 20.

It’s something world doubles No.1 Strycova hopes to see more of.

“It’s also good for the tour and for the people, because doubles can be really enjoyable and exciting for the people,” she said.

“It was a really entertaining match for us and I … could feel that the people enjoyed it a lot.

“I was very surprised that so many people came today – well, not surprised, because Ash was playing.”

-with AAP