Kaylee McKeown's staggering call after narrowly missing world record at Olympic swimming trials

Kaylee McKeown has sent a scary warning to her rivals ahead of the Paris Olympics, admitting she was disappointed to swim the second-fastest 100m backstroke time in swimming history on Tuesday night. The Aussie superstar came within 0.08 seconds of breaking her own world record at the Olympic selection trials in Brisbane, but made the startling confession she wasn't happy.

"I'm a little bit disappointed," McKeown said after winning in 57.41 seconds - just shy of her world record of 57.33 set in Budapest last October. "But I have booked myself another ticket to Paris so that's just another chance to go faster."

The 22-year-old now holds the six fastest times in the history of the women's 100m backstroke. But the reigning Olympic 100m and 200m backstroke champion may have been hampered by the fact she has added the 200m individual medley to her program for the Paris Games.

On Monday night she set a Commonwealth record in the medley, but it may have denied her the 100m world record just 24 hours later. "If you're going to get up and do a 200 (medley) at max effort, you're not going to come in the next day being refreshed - no matter what you do," she said. "The Olympics is just like that. If all goes to plan I will have nine individual events plus relays, so I have got to put myself in harm's way here."

Mollie O'Callaghan books Olympic spot ahead of freestyle events

Mollie O'Callaghan, who is more known for her freestyle feats, finished second behind McKeown in the 100m backstroke in 57.88. She secured a spot at the Olympics in what she described as her "fun event", but admitted she might opt out of it at the Games because of her packed freestyle schedule.

"I don't know yet. It really depends on if I qualify for the next few (freestyle) events, that's the main thing," the 200m freestyle world record holder said. "The 100 backstroke for me is a fun event, I don't really train for it, so to go out there and do a 57 is just amazing."

O'Callaghan enters Wednesday's women's 200m freestyle as world-record holder in the event. And that fact puts her on edge.

"(I'm) very, very nervous," she admitted. "There's a lot of pressure riding on this event, especially having the world record in it. And especially a lot of pressure from myself, I'm my biggest critic. Whatever happens, happens. I would really love to make the team on this event and do the best job I can."

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It seems absurd to suggest O'Callaghan might miss selection for the Olympics for the event in which she is the fastest woman of all time. But Australia has such depth in the 200m freestyle that the 20-year-old knows it's not beyond the realms of possibility.

Ariarne Titmus is the reigning Olympic champion, while McKeown will also race the 20m freestyle. Renowned sprinters Shayna Jack and Meg Harris will also feature, as will Brianna Throssell - who helped O'Callaghan, Titmus and Jack set a world record in the 4x200m freestyle relay at last year's world championships in Japan.

Mitch Larkin looking to make Aussie Olympic swimming history

Meanwhile, Mitch Larkin finished fourth in the men's 100m backstroke final, missing his first chance at creating history by becoming the first Australian man selected for four Olympic Games. Isaac Cooper won in 53.46 ahead of Bradley Woodward (53.53), Enoch Robb (54.14) and Larkin (54.22), who still has the 200m backstroke to come on Friday.

All four swimmers were outside of the automatic Olympic qualifying time set by Swimming Australia, with selection now at the discretion of officials. "We just have to see what Swimming Australia will decide," Cooper said.

with AAP