Sydney - Defending champion Emily Seebohm missed out on qualifying for her seventh world championships on Friday after only managing third in the 200m backstroke behind next-gen stars Kaylee McKeown and Minna Atherton at the Australian trials.
Seebohm has been a dominant force in the event, winning the world title in 2015 and 2017, but she had no answer to the teenage pair with McKeown, 17, hitting the wall in 2:06.35, a new personal best.
Atherton, 19, came second with her 27-year-old training partner Seebohm, whose lead-up was disrupted by a bout of food poisoning, a distant third.
The same pair booked the two qualifying spots in the 100m backstroke, with Seebohm again missing out on a chance to be in South Korea next month.
"That definitely didn't feel easy," said McKeown, who also won the 200m individual medley this week.
"My coach put down a really good race plan and I tried my best to stick with it. I'm really happy with that and excited to see what comes next."
In contrast to Seebohm, fellow veteran Cate Campbell followed up her super-fast 100m freestyle win by touching first (24.05) ahead of sister Bronte (24.17), the 2015 world champion, in the 50m splash and dash.
"My dream was always to be an Australian Dolphin (international) and every now and then I still have to pinch myself that I'm still living that dream," said 27-year-old Cate, who will be a hot medal favourite in both events.
"I can't wait to be part of it (the championships) this year."
Her main challenger in South Korea is expected to be Swedish world record holder Sarah Sjostrom.
In other events on the last day of the six-day trials, Olympic champion Kyle Chalmers completed the treble by winning the 50m freestyle in 22.09 ahead of Cameron McEvoy to go with his 100m and 200m victories.
David Morgan and Matthew Temple jointly won the 100m butterfly but their 51.47 - personal bests for both - was fractionally outside the automatic qualifying time.
But Australian record holder Thomas Fraser-Holmes ensured he will be at the world championships by winning the 400m individual medley in 4:14.68.