Nadal advances to second round, Venus orbits out of Aus Open

The Spanish world number one was hampered by a knee injury at the tail-end of the 2017 season, and he entered the opening Grand Slam of the year without playing a warm-up event. But he wore no strapping and appeared to move freely in a ruthless 6-1, 6-1, 6-1 demolition of the Dominican Republic's Victor Estrella Burgos in just 94 minutes on Rod Laver Arena.

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

"I want to enjoy every moment I'm here on this court."

Second seeded Caroline Wozniacki also comfortably progressed with a straight sets win over Romanian Mihaela Buzarnescu as she searches for a maiden Grand Slam crown.

But there was no celebrating for fifth seed Williams, who was stunned by Swiss star Belinda Bencic, fresh from winning the Hopman Cup with Roger Federer.

Fellow American and US Open champion Sloane Stephens was also sent packing, along with big-hitter CoCo Vandeweghe, the 10th seed and a semi-finalist last year.

And the US misery was compounded on the men's side with eighth seed Jack Sock toppled by Japan's Yuichi Sugita and 16th-seed John Isner sent home by Australian Matthew Ebden.

Third seed Grigor Dimitrov survived, as did volatile Australian Nick Kyrgios, who collected a code violation for swearing at the crowd.

Seven-time Grand Slam winner Williams, in her 77th major, struggled against a player who had never before beaten her to go down 6-3, 7-5 and deprive 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. "I don't think I played a bad match. She just played above and beyond," said the 37-year-old.