MELBOURNE • Venus Williams and US Open champion Sloane Stephens led a string of seeds sent tumbling out of the Australian Open yesterday, offering a reminder of how quickly things can change in tennis.

Fifth seed Venus, who lost in the final to sister Serena last year, was stunned by unseeded Swiss Belinda Bencic, fresh from winning the Hopman Cup with Roger Federer.

Seven-time Grand Slam singles winner Venus, playing in her 77th Major, struggled against a player who had never beaten her in four previous attempts, going down 3-6, 5-7 and depriving the tournament of one of its biggest names.

It is the first time since 1997 that there will be neither of the Williams sisters in the second round, with Serena not playing after giving birth to her first child.

Venus had been aiming to go deep into the tournament after a resurgent 2017 when she featured in the title deciders at Wimbledon and the WTA Finals in Singapore.

But she insisted she was not extra disappointed, given what she achieved last season.

"Last year is last year. This is like a new year. You can't live in the previous year," said the 37-year-old. "I don't think I played a bad match. She just played above and beyond."

World No. 78 Bencic said featuring with Federer at the Hopman Cup had helped a lot, with the Swiss legend giving her advice and tips. She even had Federer's parents in her box at the Rod Laver Arena.

"I think all the week it was so great learning from him on the court or off the court," the 20-year-old said, adding she spoke to him briefly after her match and he "was very happy for me".

Stephens has had little to cheer about since winning the US Open title in September and that continued yesterday, with the 13th seed crashing out to Chinese No. 2 Zhang Shuai.

The struggling Stephens committed 29 unforced errors on an overcast and windy day and has now not won since Flushing Meadows.

"I'm not going to get too down," she said after her 6-2, 6-7 (2-7), 2-6 defeat - her eighth straight loss.

"It's not tough times. It's just a learning experience. You know, it's a long journey. Like I said, this year, it's a new year, only the second tournament of the year. It's a long road and long season ahead."

The 2014 runner-up in Melbourne and 24th seed Dominika Cibulkova of Slovakia also crashed out, losing 2-6, 2-6 to Kaia Kanepi of Estonia.

On the men's side, eighth seed Jack Sock made 52 unforced errors as Japan's Yuichi Sugita sent him packing 6-1, 7-6 (7-4), 5-7, 6-3.

Compatriot and 16th seed John Isner was toppled by Australian Matthew Ebden 4-6, 6-3, 3-6, 3-6 while last year's US Open finalist and 11th seed Kevin Anderson was bundled out in a thriller by Britain's Kyle Edmund 7-6 (7-4), 3-6, 6-3, 3-6, 4-6 .

But there were no problems for world No. 1 Rafael Nadal, who dispelled any knee injury worries in a ruthless 6-1, 6-1, 6-1 demolition of Dominican Victor Estrella Burgos.

The 31-year-old Spaniard entered the opening Grand Slam of the year without playing a warm-up event, but he wore no strapping and progressed after just 94 minutes.

"I'm very happy to be back, it's a very important beginning for me," he said, adding that he had experienced "no problems" with his knee during the match. "It's good news for me."

AGENCE FRANCE-PRESSE

AUSTRALIAN OPEN

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