Seeds Alexander Zverev and Casper Ruud finished up four hour-plus marathons at almost exactly the same time to advance.
Tournament No. 6 Zverev fought off a furious attack from Slovak qualifier Lukas Klein, with the German winner admitting he was barely hanging in the contest, which he won 7-5, 3-6, 4-6, 7-6 (5), 7-6 (10-7)
The German, a second-round loser here a year ago, earned his 400th tour victory and has won his last 17 matches against qualifiers.
But Klein out-hit the seed 80 winners to 49 for Zverev.
Ruud, seeded 11th, managed a victory over Australian Max Purcell 6-3, 6-7 (5), 6-3, 3-6, 7-6 (10-7) .
“I would have much rather won in an hour and a half, but what can I do,” Zverev said.
“He played incredible, hitting every single ball as hard as he could frm both sides.
“I didn’t know what to do a lot of the time. He probably deserved to win this match more than I did, but that’s how tennis goes sometimes.”
No. 160 Klein left the seed trailing two set to one before the struggle finally ended in the final-set deciding tiebreaker.
“I was thinking their is a flight tonight at 11 p.m. to Dubai and then home,” Zverev admitted.
“A lot of the time I was just a spectator out there. The match was often in his hands.”
Ruud equalled his disappointing 2023 second round after starting 12 months ago as second seed.
The Norwegian also found himself involved in a fifth-set dogfight which went to the 10-point tiebreak.
“It was an incredible match which could have gone either way,’ the winner said. “He’s a tricky and good player.
“He plays fast and plays serve-and-volley, which is unorthodox these days. We’re not used to playing players like that.
“I was lucky a few points went my way near the end,” Ruud said after sealing victory on his first match point as Purcell drove a return long.
Carlos Alcaraz needed three and a half hours to deal with Italy’s determined Lorenzo Sonego before finally posting a 6-4, 6-7 (3), 6-3, 7-6 (3) win into the third round.
The Spaniard was playing the 200 Tour match of his two-and-a-half year career, finishing up with a vicious smash at the net on match point.
“I’m really happy with the performance today,” the 20-year-old winner said.
“He was playing at a great level.
“The match was a little tricky today with the wind. That can make it tough to play your best.
“But we had some good points, it was a great match.”
Brit Cam Norrie survived three rain interruptions as he rallied from two sets to love down for a 3-6, 6-7 (4), 6-2, 6-4, 6-4 victory over Italian qualifier Giulio Zeppieri.
But Tommy Paul of the US ended the hopes of Britain’s Jack Draper, handing out a 6-2, 3-6, 6-3, 7-5 defeat.
American Alex Michelsen sprang a 4-6, 6-3, 6-4, 6-4 comeback surprise on Jiri Lehecka, sending out the Czech who won the Adelaide title at the weekend.
