Defending champion Roger Federer reached the Australian Open third round for a 20th straight year but was made to battle hard by Britain's Dan Evans before winning 7-6, 7-6, 6-3.
The 20-time grand slam champion, who is gunning for a record seventh Melbourne Park title and third in a row, had breezed past Denis Istomin in the first round, but was given a much tougher examination by the world No 189.
"I think if I could have pulled away early in the match it might have been different," said the 37-year-old Swiss who needed 2 hours 35 minutes to get past his 28-year-old opponent.
Evans, whose ranking plummeted from a career-high 41 after he was slapped with a year-long ban for testing positive to cocaine in April 2017, played almost flawless tennis to stave off a set point on his way to forcing a first set tie-break.
He even had the temerity to lead 5-3 in the breaker before Federer stepped up a gear and reeled off the next four points with a cry of "Come on!" as he secured a hard-fought opening set after exactly one hour.
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It was harsh on Evans who had committed only two unforced errors and constantly put the third seed under pressure with his scampering, attacking game and flurry of winners off both wings.
The plucky Evans, who had covered acres of ground and found the lines brilliantly, needed treatment for blisters on both feet before the second set started and immediately was broken.
But he refused to lie down and broke back as Federer served for the set to force another tie-break.
"I thought I might have pulled away midway through the second set," added Federer. "But I couldn't, to his credit. He played well."
The Swiss star hasn't often needed luck during his unparallelled career but he took advantage of some in the third set to finally ease the pressure.
Holding break point at 2-1, he barely scooped up a half-volley which grabbed the net cord and toppled over forcing Evans to go long.
A service game to love followed to put Federer 4-1 up and the brave resistance of Evans was finally broken.
The veteran will next play either France's Gael Monfils, seeded 30, or American Taylor Fritz in the last 32.
Defending women's champion Caroline Wozniacki eased past her second-round opponent Johanna Larsson 6-1, 6-3 in a one-sided clash.
The victory sets up the potential for an enthralling third round encounter between the Dane and Maria Sharapova, who meets Rebecca Peterson in the second round.
Wozniacki, seeded third, took just over an hour to secure her second consecutive straight-sets win.
Dane Wozniacki, who is battling rheumatoid arthritis, steamrolled past her Swedish opponent as she bids to become the first woman to defend the title since Victoria Azarenka in 2013.
"I thought I started pretty well, started aggressively, but she started making less errors and I was just trying to stay consistent," Wozniacki said.
Meanwhile, Sloane Stephens, who endured a horror run at Melbourne Park since reaching the semi-final in 2013, exiting in the first round in 2015, 2016 and 2018, swatted aside former doubles partner Timea Babos 6-3, 6-1.
It kept her on a collision course with world No 2 Angelique Kerber in the quarter-finals.
Fifth seed Kevin Anderson lost his second round match to Frances Tiafoe 4-6, 6-4, 6-4, 7-5 in a major upset on the third day of the grand slam.
The Wimbledon finalist took a medical time-out mid-way through the four-set match before becoming the highest ranked player to be ousted from the first major of the year.
After sealing match point against the South African, Tiafoe slapped his right bicep, thumped his chest and roared at the terraces.
"It means the world to me, I lost to Kevin three times last year. I would love to get to the second week of a Slam and if you guys get behind me like you did again, then it's going to be pretty easy for me," Tiafoe said.
American Tiafoe, ranked 39 in the world, will play Italy's Andreas Seppi in the third round, which will at least equal his best performance at a Grand Slam, having made the third round of Wimbledon last year.
💪BIG FOE 💪@FTiafoe shocks 6 seed Kevin Anderson 4-6 6-4 6-4 7-5.#AusOpen pic.twitter.com/2AthQLrBY1
— #AusOpen (@AustralianOpen) January 16, 2019
Sixth seed and last year's Australian Open runner-up Marin Cilic ground out a tough four sets win over American Mackenzie McDonald to move into the third round Thursday.
The Croat, who lost an epic final in five sets to Roger Federer a year ago, needed 3hr 37min to get past the 23-year-old 7-5, 6-7, 6-4, 6-4.
"Every single time the atmosphere here is amazing," said Cilic, who has been struggling with a knee injury.
"Mackenzie played unbelievable tennis today, he was hitting from the back ridiculously well. I had to work hard to win this one and I'm extremely pleased."
The former US Open champion, who will next play either Spanish 26th seed Fernando Verdasco or Radu Albot of Moldova, said the knee was still not 100 per cent.
"It's getting better but I feel that if could improve, so I'm hoping with a couple of matches and getting used to the conditions it's going to get better," he said.
"I'm hitting the ball well and enjoying my time on the court and these two matches have been great for me."
Australia's top-ranked player Ashleigh Barty beat Wang Yafan 6-2, 6-3 in a straight-forward affair on Wednesday, propelling the home country's leading prospect into the third round.
The 15th-seeded Barty is the highest ranked local player -- either man or woman -- in the tournament and is known for her court craft and is an accomplished doubles player, while she has also played elite-level cricket.
"I felt like today was pretty clean, except for a couple of games where I got passive," Barty told reporters.
The 22-year-old will play Greece's Maria Sakkari in the third round.
She is one of a rapidly depleting list of local players at the tournament where Australians have had limited success despite boasting several Grand Slam singles champions like Samantha Stosur, Lleyton Hewitt and Pat Rafter since the 1990s.
No Australian man or woman has won the singles title at their home Grand Slam since the 1970s. The last women's finalist was Wendy Turnbull in 1980, while Hewitt lost the 2005 final to Russia's Marat Safin.
An injury-hampered Nick Kyrgios crashed out of the Australian Open first round on Tuesday in straight sets, leaving further doubts as to whether the 23-year-old can realise his potential.
Australia's top-ranked male prospect, Alex de Minaur, is scheduled to play his second round match against Switzerland's Henri Laaksonen later on Wednesday.
