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.
After withdrawing from Abu Dhabi and Brisbane to delay his start to the 2018 season, there was cause for concern that the Spaniard hadn’t fully recovered from the knee injury that forced him to pull out of the ATP Finals last November (he only played his first match there).
But it’s fair to say that most of those concerns dissipated following a stellar opening win for Nadal on Rod Laver Arena on Monday night.
He next takes on Argentina’s Leonardo Mayer.
Here are three things learned from Nadal’s success over Estrella Burgos…
KNEE SEEMS FINE
Against a grinder like Estrella Burgos, Nadal looked comfortable running down balls, showcasing a great all-court game against the Dominican, who barring that one service game in which he broke Nadal while he was serving for the second set, barely troubled the world No. 1.
Reassuring everyone in press, Nadal said after his match when asked how his body was feeling: “Good. If I don’t feel myself ready, I will not be here.”
Asked about the knee specifically, the Mallorcan said: “No problems.”
According to the Australian Open website statistics, Nadal’s average first serve speed was 199km/hr against Estrella Burgos. That is US Open 2010-level serving from the Spaniard. He also landed 73 per cent of his first serves in and won a remarkable 67 per cent of the points on his SECOND serve (77% on his first).
If he serves like that throughout the fortnight, on a fast surface like Melbourne, he could save himself lots of energy and spend less time running on that recently-injured right knee.
For the most part, and for someone who started his preseason training later than usual to recover his knee, Nadal was hitting the ball clean, firing 28 winners during his 94-minute win. His down-the-line shots were finding the lines nicely and despite his 11 forehand unforced errors, he should be pleased with how his first match in two months unfolded.
THE NUMBERS GAME
Nadal is now 52-11 win-loss at the Australian Open.
He is bidding to become only the sixth player in the Open Era to win the Australian Open after winning the US Open in the previous season.
Nadal is bidding to win his second Australian Open title and become the first man in the Open Era – and only the third man in history – to win each of the four Grand Slam titles twice. Roy Emerson and Rod Laver are the only players to have won each Grand Slam on two or more occasions.
— #AusOpen (@AustralianOpen) January 15, 2018
World number five Venus Williams and US Open champion Sloane Stephens were high-profile casualties on day one of the Australian Open Monday, but Roland Garros winner Jelena Ostapenko survived.
Williams, who lost in the final to sister Serena last year, was stunned by Swiss star Belinda Bencic, fresh from winning the Hopman Cup with Roger Federer.
The seven-time Grand Slam winner, 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 would like to have played someone easier,” said Bencic.
“When I was a little girl watching on TV I would never imagine I would play them (the Williams).”
Also out of the opening Grand Slam of the year is American big-hitter CoCo Vandeweghe, a semi-finalist last year at Melbourne Park and Flushing Meadow.
She slumped out to Hungary’s Timea Babos 7-6 (7/4), 6-2.
Stephens’ poor run since winning at Flushing Meadows in September continued, with the 13th seed crashing out to Chinese number two Zhang Shuai, who made the last eight two years ago.
The frustrated American put in an error-strewn performance on an overcast and windy Melbourne day and has now not won in seven matches.
“I’m not going to get too down,” said Stephens after her 2-6, 7-6 (7/2), 6-2 defeat.
“I’m just going to stay positive and keep working to get back in the best shape and best place possible to do well for my next tournaments.”
There was better luck for Ostapenko, who saw off Francesca Schiavone 6-1, 6-4.
The seventh seed raced through the first set on Rod Laver Arena against the veteran Italian who was bizarrely wearing a back brace on the outside of her shirt.
She was 4-1 down in the second before knuckling down to race home and a second round clash with China’s Duan Yingying.
“I knew before the match that it’s not going to be easy. She’s very experienced player and she’s very long time on tour,” said the Latvian.
“I knew I had to play really aggressive and stay very consistent.”
Also into the next round with a straight sets win was German 12th seed Julia Goerges, who won the lead-up Auckland Classic and is now on a 15-match unbeaten streak having ended 2017 with victories at Moscow and Zhuhai.
World number two Caroline Wozniacki, who lost to Goerges in that New Zealand decider, plays later Monday, along with men’s top seed Rafael Nadal.
Sixteen-time Grand Slam champion Nadal insists he is feeling fine despite struggling with a knee injury and ready to go deep at an event that he has only won once — in 2009 — among his string of major triumphs.
This is despite a chequered lead-up that prevented him playing a warm-up tournament for the first time ever ahead of the opening Grand Slam of the year.
“It’s a new situation for me. But I feel good,” said the 31-year-old, who first played at Melbourne Park in 2004.
Nadal, who faces the Dominican Republic’s Victor Estrella Burgos in a night match on Rod Laver Arena, lost an epic Australian Open final last year to Roger Federer, who gets his campaign under way on Tuesday.
Fellow multiple Grand Slam winner Novak Djokovic, seeded 14, also starts on Tuesday, along with former world number one Maria Sharapova and top seed Simona Halep.
Among men safely through to the next round are 31st seed Pablo Cuevas and Ukrainian Alexandr Dolgopolov.