Alcaraz outlasts Sonego on day of tests at Australian Open - ESPN

No. 2 Carlos Alcaraz endured a tricky test before finding his groove to overcome Italian Lorenzo Sonego 6-4, 6-7 (3), 6-3, 7-6 (3) at the Australian Open on Thursday and make the third round on a day of epic battles.

As Casper Ruud, Alexander Zverev, Cameron Norrie and Hubert Hurkacz all huffed and puffed to five-set wins over lower-ranked opponents, the 20-year-old Spaniard was tested by the wind against the unseeded Sonego.

"I'm really happy with my performance today," Alcaraz said. "I think both of us played a really high level, high intensity. The match was a little bit tricky with the wind and the sun."

The two-time Grand Slam champion, who missed last year's tournament because of injury, took the opening set with a single break then in the next set let Sonego off the hook in the ninth game and was unable to recover from 5-1 down in the tiebreak.

Sonego, ranked No. 46 in the world, won the pair's only previous clash in 2021, when Alcaraz was outside the top 50. But the 28-year-old was put through the wringer by his vastly improved opponent's heavy forehands to lose the third set.

In a fourth set where both players were at their entertaining best, Sonego surrendered serve early on, but Alcaraz raised his game to reel off the points in the tiebreak and go through in style.

"It was tough to play your best, but we tried to stay there all the time, even if I lost the second set," said Alcaraz, who will face Chinese wild card Juncheng Shang next after he ousted India's Sumit Nagal 2-6, 6-3, 7-5, 6-4.

It will be the first time on tour that Alcaraz has faced a younger player.

"He beat some big guys," Alcaraz said of Shang's run to the semifinals in Hong Kong earlier this month. "So I know he has the level. He's already there."

No. 6 Zverev survived a mighty scare earlier Thursday as the former semifinalist dug deep to beat Slovak qualifier Lukas Klein 7-5, 3-6, 4-6, 7-6 (5), 7-6 (7) and move into the third round.

Rain forced the 4½-hour contest to be completed under the roof at John Cain Arena, and Zverev found himself in huge trouble as world No. 163 Klein turned up the pressure after losing the opening set to take the next two.

"I would have much rather won in an hour and a half, but what can I do?" Zverev said. "He played incredible, was hitting every ball as hard as he could from both sides. I didn't really know what to do a lot of the times.

"To be honest, he probably deserved to win more than me. That's how tennis goes sometimes. I'm happy that I'm through, but his ranking is no value to how he's playing."

The 25-year-old Klein, whose only previous Grand Slam main draw appearance was at Wimbledon in 2022, was inching toward his first career top-10 win but squandered the chance to break at 4-4 in the fourth set, much to Zverev's relief.

Zverev leveled the contest as Klein frittered away a 3-1 lead in the tiebreak. The 26-year-old German swapped breaks with his opponent early in the decider before holding his nerve in a tiebreak to prevail.

He will next face American Alex Michelsen, who defeated No. 23 Jiri Lehecka 4-6, 6-3, 6-4, 6-4.

No. 11 Ruud also went the distance, edging Max Purcell 6-3, 6-7 (5), 6-3, 3-6, 7-6 (7).

"That's a typical match you could end up losing," Ruud told reporters. "Today I didn't have to save match point, but he was basically only three points away from winning."

Norrie, the No. 19 seed, went five sets as well, coming from two sets down to beat Italian qualifier Giulio Zeppieri 3-6, 6-7 (4), 6-2, 6-4, 6-4. Norrie will face Ruud in the third round.

No. 9 Hurkacz also dropped two sets but battled through to beat Czech qualifier Jakub Mensik 6-7 (9), 6-1, 5-7, 6-1, 6-3.

Holger Rune's hopes of bettering last year's run to the fourth round were shattered by Arthur Cazaux, as the French wild card won 7-6 (4), 6-4, 4-6, 6-3.

Cazaux was not ranked high enough to even get into qualifying at Melbourne Park last year but outplayed the Danish No. 8 seed to record his second win in his Australian Open debut and set up a clash with Dutchman Tallon Griekspoor.

"It was a crazy match," said the 21-year-old Cazaux. "Holger is a wonderful player. I knew it would be a big fight, and I was ready. I'm so happy.

"Tennis is a show and I gave all I had in me."

Jack Draper was unable to replicate his win over Tommy Paul in Adelaide last week, and the American No. 14 seed progressed 6-2, 3-6, 6-3, 7-5. No. 13 Grigor Dimitrov dropped a set but overcame Thanasi Kokkinakis 6-3, 6-2, 4-6, 6-4, No. 21 Ugo Humbert reached the third round with a 6-2, 5-7, 6-1, 7-6 (3) win over Zhang Zhizhen, and No. 27 Felix Auger-Aliassime defeated Hugo Grenier 6-1, 3-6, 6-1, 6-2.

Reuters and The Associated Press contributed to this report.