In contrast, men’s top seed Rafa Nadal looked outstanding in his straight sets win over Victor Estrella Burgos, while the impressive Belinca Bencic beat Venus Williams to book her place in the second round.
Here, we pick out three who shone and three who struggled on day one.
England’s Kyle Edmund pulled off the biggest victory of his career with a five-set win over Kevin Anderson.
The 23-year-old stepped up in the absence of the injured Andy Murray to recover from two sets down and beat the South African 6-7, 6-3, 3-6, 6-3, 6-4.
Edmund looked flawless and sealed his win after three hours and 59 minutes.
He will face Denis Istomin of Uzbekistan in the second round on Tuesday – the man who beat Novak Djokovic at the same stage in the last edition of the tournament.
Swiss star Belinda Bencic stunned Venus Williams in straight sets 6-3, 7-5 to advance to the second round at Melbourne Park.
The 20-year-old was outstanding as she dispatched the American with ease to set up a clash with Luksika Kumkhum on Wednesday morning.
It is the first time since 1997 that neither Williams sisters feature in the second round of the Australian Open.
Rafael Nadal showed no signs of injury concerns as he cruised into the next round.
The World No1 was curtailed by a knee injury at the end of the 2017 season, and he arrived in Melbourne without playing a warm-up event.
However, he dispatched the Dominican Republic’s Victor Estrella Burgos 6-1, 6-1, 6-1 with minimal fuss, taking just 94 minutes to get the result.
Sloane Stephens’ dire run of form continued after she was beaten by Zhang Shuai of China 2-6, 7-6, 6-2.
The 13th seed produced another disappointing performance and has not won in seven matches now.
Stephens returned from a career changing injury to win the US Open in September but has struggled with form and confidence since her success at Flushing Meadows.
Last year’s semi-finalist Coco Vandeweghe crashed out of the Australian Open after a horror first round showing against Timea Babos.
The 10th seed, who also made the last four at the US Open in 2017, was beaten in straight sets by Hungary’s Babos 7-6, 6-2.
She was the third big-name American to be sent packing on day one – alongside Venus Williams and Sloane Stephens.
The World No51 Hungarian took an hour and 46 minutes to beat an inconsistent Vandeweghe, who committed 28 unforced errors.
Jack Sock tumbled out of the Australian Open after losing 6-1, 7-6, 5-7, 6-3 to Yuichi Sugita of Japan.
The eighth seed was defeated in two-and-half-hours by the World No41 ranked Sugita.
The American had suffered a minor hip injury during the Hopman Cup earlier this month – and bowed out in the second round of the Auckland Classic a week later.
Sock hit 52 unforced errors en route to his defeat against Sugita, who will now face Ivo Karlovic of Croatia in the next round.
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