Wimbledon champion Murray, three times a finalist in Melbourne, is playing his first grand slam since back surgery in September ruled him out of the final two months of last season.
He has dropped only one place in the standings in that time, behind Spain’s David Ferrer, and cannot face either Nadal or three-times defending champion Novak Djokovic until the semi-finals.
Argentina’s Juan Martin del Potro is the fifth seed, ahead of 17-times grand slam champion Roger Federer, with Tomas Berdych, Stanislas Wawrinka, Richard Gasquet and Jo-Wilfried Tsonga rounding off the top ten.
The top 28 seeds correspond directly to the rankings but Canada’s Vasek Pospisil, who lost in qualifying 12 months ago, is elevated to 29th because of Jurgen Melzer’s withdrawal through injury. Spain’s Fernando Verdasco is the 32nd and final seed.
Williams, who warmed up for the Australian Open by winning the title in Brisbane last week, heads defending champion Victoria Azarenka and fit-again Maria Sharapova in the women’s seedings. Sharapova missed the final part of last season, including the US Open, because of shoulder problems.
Last year’s beaten finalist, Li Na, is fourth seed ahead of Pole Agnieszka Radwanksa, Petra Kvitova, Sara Errani, Jelena Jankovic, Angelique Kerber and Caroline Wozniacki.
American Sloane Stephens, who beat Williams to reach the semi-finals last year, is 13th with Ana Ivanovic 14th and home hopeful Sam Stosur 17th. Canadian teenager Eugenie Bouchard is a seed for the first time at a grand slam at 30, with injured world No 18 Maria Kirilenko of Russia the only one missing from the top 32.
Great Britain’s Dan Evans is still battling to get into the main draw for the first grand slam of the year and yesterday was the sole British survivor on the first day of qualifying. Evans pulled away against Chinese Taipei’s Huang Liang-chi after a tight opening to win 6-1, 6-2. The 23-year-old from Birmingham next meets Hungarian Marton Fucsovics, who is ranked 33 places below Evans’ 149.
Evans needs to win two more matches to reach the main draw, and he said: “I’m pretty confident I’ll come through but quite a lot can happen through the next two matches.”
Evans began the year by qualifying at the ATP Tour event in Doha, where he took a set from world No 24 Ernests Gulbis in the first round.
The other two Britons in the men’s draw both lost, James Ward to Italy’s Andrea Arnaboldi 7-6 (7/2), 6-4 and Dan Cox 6-4, 6-1 to American Denis Kudla.
Women’s qualifying begins today, with Heather Watson, Johanna Konta and Tara Moore the three Britons in action. Watson meets Australian Arina Rodionova, Konta, who only just missed out on a place in the main draw on ranking, faces American Grace Min, while Moore takes on Japan’s Erika Sema.
Murray and Laura Robson are Britain’s only two direct singles entrants. Robson remains a doubt because of a left wrist problem that forced her to retire from her first-round match in Hobart this week but the 19-year-old did practise at Melbourne Park on Wednesday.
Murray will warm up for the tournament with an exhibition match against Lleyton Hewitt at Kooyong tomorrow.