World number five Juan Martin del Potro will miss the Australian Open in January as he continues his recovery from a fractured kneecap.

The Argentine, 30, sustained the injury in a heavy fall at the Shanghai Masters in October.

“Recovery is going great and I will tell you later where I will be making my comeback,” the 2009 US Open champion said on social media.

“It won’t happen in Australia, but I’m happy with my progress.”

Del Potro has been plagued by injuries since winning his only Grand Slam, and has had three operations on a wrist problem, which left him struggling to use his backhand.

But he had a successful 2018, beating Roger Federer to claim the BNP Paribas Open title at Indian Wells in March, before reaching the semi-finals of the French Open, the last eight at Wimbledon and the final of the US Open, where he was beaten by Novak Djokovic.

Tennis greats Roger Federer and Serena Williams will meet on court for the first time at the Hopman Cup on Tuesday when Switzerland face the USA in Perth.

They will play in men’s and women’s singles rubbers before meeting in the mixed doubles alongside partners Belinda Bencic and Frances Tiafoe.

Federer and Williams, both 37, have won a combined 43 Grand Slam titles.

“It is very exciting for both of us and I hope a lot of tennis fans tune in and watch it,” said Federer.

Williams said it was “like a dream come true”. She added: “I have been looking forward to it. This is so cool.”

The match has been described as the most anticipated contest involving a male and female player since the “Battle of the Sexes” in 1973, when 39-time Grand Slam champion Billie Jean King beat former men’s world number one Bobby Riggs in straight sets.

Despite their concurrent careers, Federer said it would be an “exaggeration” to say he knew Williams well.

“I admire everything she’s done on and off the court, we are both fierce competitors and we always want to win,” he said.

“It is going to be one time, probably never again. She is one of the biggest champions in our sport ever – men and women combined – so it is great to be playing against her.”

The Hopman Cup comprises two singles and a mixed doubles match between nations in a round-robin format with two groups of four. The winners of each group will contest Saturday’s final.

Federer and Bencic beat Britain’s Cameron Norrie and Katie Boulter in their opening round-robin tie, while the USA lost to Greece on Monday despite Williams winning her singles tie.

Switzerland are the defending champions, Federer and Bencic having won the event in Perth in January 2018.

British number four Harriet Dart came from behind to beat Australian wildcard Priscilla Hon and reach the second round of the Brisbane International.

The 22-year-old, who progressed from the qualifying rounds, won 1-6 6-3 6-4.

Dart will play Latvian eighth seed Anastasija Sevastova or Australia’s Daria Gavrilova next.

“I’m really pleased to get the win. Priscilla played really good and it took me a while to get out of the blocks,” Dart said.

“Everyone is fighting for every point so I had to keep doing what I was doing.”

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Dart started the year ranked 307th in the world but will end it in 149th, having won ITF titles in Altenkirchen and Oslo.

She made her Grand Slam debut at Wimbledon in 2018, losing in three sets to former world number one Karolina Pliskova in the first round.

Dart beat German former world top-10 player Andrea Petkovic and Kateryna Kozlova of Ukraine in qualifying in Brisbane.

Elsewhere, Czech Pliskova came from a set and a break down to defeat Yulia Putintseva, while world number 10 Daria Kasatkina fell to a shock defeat by Australian wildcard Kimberly Birrell.

Dutch sixth seed Kiki Bertens beat Belgium’s Elise Mertens to set up a second-round meeting with Croatia’s Donna Vekic, who overcame Magdalena Rybarikova of Slovakia.

In the men’s singles, former champions Milos Raonic and Grigor Dimitrov are into the second round after defeating Aljaz Bedene and Yoshihito Nishioka respectively.