MELBOURNE: Ashleigh Barty will be hot favourite to win her home Australian Open for the first time, but even with Serena Williams absent the world number one faces threats from all angles.

For the first time in a quarter of a century the first Grand Slam of the year will not feature either of the Williams sisters -- Serena would have been pursuing a record-equalling 24th major crown but she is not fit.

With defending champion Naomi Osaka still working her way back to top form and fitness after a long break, the 25-year-old Barty has emerged as the clear favourite at Melbourne Park.

Like her rival Osaka, Barty was dumped out of the third round of the US Open in September and did not play the rest of the year, returning home to Australia because of the coronavirus pandemic.

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Unlike the Japanese star, who pulled out of a warm-up tournament last week saying her "body got a shock" after playing her first matches for four months, Barty appears to be back in the groove already.

Barty won the French Open in 2019 and Wimbledon last year but her best performance in Melbourne was reaching the semi-finals in 2020, where she lost to eventual champion Sofia Kenin.

However, she fired a warning to the rest of the Australian Open field on Sunday, claiming the singles and doubles titles at the Adelaide International.

Barty pulled out of this week's Sydney Classic, explaining that she needed to recover from her exploits, but said that her 14th career singles crown was a huge confidence boost.

"When my back was against the wall I was able to produce some pretty good stuff," she told the WTA.

"Pre-seasons are good but you never quite know where that level is until you test yourself against the very best.

"And it's been really nice to have some good hit-outs this week and I feel like I'm ready."

Halep, Muguruza threaten

Men's tennis has been dominated by the "Big Three" of Novak Djokovic, Rafael Nadal and Roger Federer, but women's tennis remains wide open.

Last year's four Grand Slams were won by four different women -- Osaka (Australian), Barbora Krejcikova (French), Barty (Wimbledon) and Emma Raducanu (US) and Osaka and Barty's early exits at the US Open underlined the point.

Osaka, a two-time Melbourne champion, went out to eventual New York finalist Leylah Fernandez, who lost to fellow unseeded teenager Raducanu in the title decider.

The Briton Raducanu, who is embarking on her first full WTA Tour season, has struggled since her stunning emergence at Flushing Meadows and last month tested positive for Covid-19.

She pulled out of a Melbourne build-up event last week saying that it was "too soon for me, having just returned from isolation".

Raducanu should be fine for the Australian Open, and Fernandez will also be there, as will another prodigious young talent in the form of 17-year-old American Coco Gauff.

But this could be the chance for the older guard to reassert themselves.

Garbine Muguruza, who lost to the American Kenin in the 2020 final, is third in the world rankings behind Barty and big-hitting Aryna Sabalenka of Belarus.

The 28-year-old Spaniard squandered two match points against Osaka last year at Melbourne Park in the last 16 and won the season-ending WTA Finals in Guadalajara.

The 30-year-old Romanian, a popular figure within women's tennis, on Sunday won her first title in 16 months following a bleak run of calf and knee problems.

"After a tough year it's always nice to have a trophy in my hands," said the Romanian.

"Physically I'm in the right place, confidence is growing," she added.