Casper Ruud on Thursday joined Rafael Nadal in making a stunning second-round exit from the Australian Open, another boost to Novak Djokovic's bid for a 22nd Grand Slam title.
On a bad day for some of the leading men's players, Ruud was always struggling against hard-hitting Jenson Brooksby, the second seed from Norway going down in four sets.
Soon after, Taylor Fritz and Alexander Zverev also became high-profile casualties.
Defending champion Nadal limped out of the tournament on day three in a shock defeat to Mackenzie McDonald and on day four it was another American who ousted Ruud.
The top two seeds are now gone in the first week at Melbourne Park, with Nadal saying on Thursday he will be out for about six to eight weeks with his hip injury.
The 39th-ranked Brooksby, who is on his Australian Open debut, will face Tommy Paul in round three after his fellow American beat Spain's Alejandro Davidovich Fokina in five sets.
"First and foremost, Casper is a warrior, I knew it would be a great battle out there," said Brooksby, 22, having prevailed 6-3, 7-5, 6-7 (4/7), 6-2.
"I'm just really proud of my mental resolve after the third-set battle didn't go my way, and to turn it around."
Ruud, who could have become world number one in Melbourne, refused to blame an abdominal injury.
"I gave it my all, but in the fourth set especially it wasn't enough," he said.
Eighth seed Fritz was also on his way home after wildcard local hope Alexei Popyrin beat him 6-7 (4/7), 7-6 (7/2), 6-4, 6-7 (6/8), 6-2.
"This is a dream and I don't want to wake up at all," said Popyrin, who was reduced to tears by the crowd chanting his name.
Zverev, the 12th seed, suffered another setback on his return from serious injury as he lost to 107th-ranked Michael Mmoh.
Safely into round three of a men's draw which was already missing injured world number one Carlos Alcaraz is Russia's fifth-seeded Andrey Rublev and ninth seed Holger Rune.
Serbia's Djokovic will step up his bid for a record-extending 10th Australian Open crown when he faces 191st-ranked French qualifier Enzo Couacaud in the night session on Rod Laver Arena.
In the women's draw, Aryna Sabalenka showed why she is a serious contender for the title by powering into the third round.
Also safely through was France's fourth seed Caroline Garcia, a 7-6 (7/5), 7-5 winner over former US Open finalist Leylah Fernandez.
Belarus's Sabalenka swept past 51st-ranked American Shelby Rogers 6-3, 6-1 in an hour and 27 minutes and faces 26th-seed Elise Mertens.
Sabalenka, who reached the semi-finals at the US Open last year, extended her 2023 unbeaten record to six matches. She won the recent Adelaide International without dropping a set.
It is a marked contrast to the start of last season when her serve completely deserted her, reducing her to tears during an Australian Open warm-up event.
Sabalenka served three aces against Rogers but, tellingly, no double faults. She talked openly about the hard work involved in turning her fortunes around.
"I worked a lot on my serve. You can't even imagine," she told reporters.
"Oh my God, I did, I think, almost everything to trying to fix my serve."
American qualifier Katie Volynets dumped out Russian world number nine Veronika Kudermetova.
The 21-year-old Volynets won 6-4, 2-6, 6-2 on Margaret Court Arena and then paid a heartfelt tribute to her extended family in war-ravaged Ukraine.
"It's really a difficult time. Before, everyone used to be able to move about the country however they want to and go on with their days," said Russian-speaking Volynets.
"And now it's just, you know, day-to-day.
"I really feel for them and to have their support through all of this is incredible."
Other seeds beaten in round two were Anett Kontaveit of Estonia, who lost to Magda Linette of Poland, and Russia's Liudmila Samsonova.