Jannik Sinner recovered from a slow start against world number 173 Tristan Schoolkate to keep his Australian Open title defence on track.
Sinner, who claimed his first major title in Melbourne last year, had not dropped a set since October’s Shanghai Masters.
But Australian Schoolkate thrilled a partisan crowd on Rod Laver Arena when he struck at 5-4 to win the opener and end Sinner’s 29-set winning streak.
However, the wildcard could not keep pace with the top seed as Sinner sped through the gears to grab a 4-6 6-4 6-1 6-3 victory and a place in the third round.
The 23-year-old is the youngest player to win nine successive men’s singles matches at the Australian Open since Novak Djokovic between 2008 and 2009.
Asked how this year felt different to his title-winning run, Sinner said: “It’s a different feeling but so many beautiful moments, on and off the court, have happened to me here. It’s different but I take it as a chance to do it again.
“It’s still a very, very long way to go. We go day by day. Seeing my level today we know that I can improve.”
Sinner is competing at the Australian Open for the first time since he failed two doping tests in March.
His doping case will be heard at the Court of Arbitration for Sport (Cas) in April after the World Anti-Doping Agency appealed appealed against the decision to clear him.
Schoolkate arrived at this year’s tournament with just two Grand Slam match wins under his belt, but he made Sinner look far from his best in the first set.
The two-time major winner struggled to deal with Schoolkate’s aggressive play at the net, with the home favourite winning 17 of his 18 net points in clinching the opener.
Sinner had to wait for 80 minutes to bring up his first break point opportunity, but he took it with both hands and it was plain sailing from there for the defending champion, who will face American Marcos Giron in the third round on Saturday.
Elsewhere on Thursday, there were upsets for Frances Tiafoe and Hubert Hurkacz.
Tiafoe, the American 17th seed, fell to a 6-7 (3-7) 6-4 3-6 6-4 6-1 defeat by Hungary’s Fabian Marozsan, ranked 59th, while world number 51 Miomir Kecmanovic moved past 18th seed Hurkacz with a 6-4 6-4 6-2 victory.
Joao Fonseca’s impressive Grand Slam debut came to an end as the Brazilian teenage sensation lost in five sets to Italy’s Lorenzo Sonego.
The 18-year-old, who Carlos Alcaraz said would be on a “list of the best players in the world”, stunned ninth seed Andrey Rublev in the first round but he lost 6-7 (6-8) 6-3 6-1 3-6 6-3 to world number 55 Sonego.
Australian home favourite Alex de Minaur claimed a straight-set win over American qualifier Tristan Boyer, while fourth seed Taylor Fritz needed just 82 minutes to beat Chilean qualifier Cristian Garin, dropping just three games during an impressive showing.
Danish 13th seed Holger Rune battled past Italy’s Matteo Berrettini with a 7-6 (7-3) 2-6 6-3 7-6 (8-6) victory.