Returning star Alexander Zverev has survived an early Australian Open scare to scramble into the second round with a five-set comeback win over qualifying lucky loser Juan Pablo Varillas.
The German 12th seed was expected to breeze past the Peruvian, ranked No.103, but instead had to claw his way to a 4-6 6-1 5-7 7-6 (7-3) 6-4 victory on Margaret Court Arena on Tuesday.
Zverev was making his return to grand slam tennis after missing most of 2022 after tearing ligaments in his ankle during a painful French Open semi-final loss to Rafael Nadal.
The former world No.2 required surgery and only made his comeback to tennis at the United Cup earlier this month.
"I'm tired but extremely happy because I've missed this for the past seven months," the 25-year-old said.
"This match alone pays off with the hard work and suffering over the last year.
"I can't wait for the rest of the tournament but either way it's already a success for me."
The 12th seed, who was a semi-finalist at Melbourne Park in 2020, never looked comfortable through the match, with his unforced error tally a costly 58.
But he did enough in the fifth set to keep his 27-year-old rival, who mostly plays on the challenger circuit, at bay.
After more than four hours, Zverev sealed the win on his second match point before letting out an emotional roar.
In a late-night finish that dragged on beyond 1am, Norway's two-time major finalist and No.2 seed Casper Ruud had quite a battle before he finally subdued Czech Tomas Machac 6-3 7-6 (8-6) 6-7 (5-7) 6-3.
Earlier, in-form American Taylor Fritz overcame a strong challenge from Nikolaz Basilashvili to also safely progress.
Fritz escaped the searing temperatures that forced officials to suspend play on outside courts for almost three hours.
But Basilashvili applied his own heat before eighth-seeded Fritz advanced with a 6-4 6-2 4-6 7-5 victory under a closed roof on John Cain Arena.
Fritz has now chalked up five straight wins this summer, including one rout of Zverev while helping pilot Team USA to United Cup glory in Sydney.
Fast emerging as an Open title threat, Fritz next faces Australian wildcard Alexei Popyrin, who ousted Taiwan's Chun-Hsin Tseng.
Fifth seed Andrey Rublev eliminated former finalist Dominic Thiem 6-3 6-4 6-2 in two hours, 10 minutes before the roof was closed on JCA.
A six-time grand slam quarter-finalist eager to take the next step at a major, 25-year-old Rublev will face either Australian qualifier Max Purcell or Finland's Emil Ruusuvuori on Thursday.
Ninth-seeded Danish teenager Holger Rune was even less troubled in a 6-2 6-3 6-4 win over Filip Krajinovic.
In other matches, Grigor Dimitrov beat Aslan Karatsev 7-6 (7-3) 7-5 6-2 in a battle of two former Open semi-finalists and five-time runner-up Andy Murray rolled back the years with the win of the day to oust Italian 13th seed Matteo Berrettini 6-3 6-3 4-6 6-7 (7-9) 7-6 (10-6).