As she nears the end of a week that’s seen her transform from gold medal hopeful to Australian sporting superstar, Ariarne Titmus has admitted she’s “absolutely buggered”.

So it’s no surprise the 20-year-old finished more than three seconds behind arch rival Katie Ledecky in 800m freestyle qualifying as the pair prepare for their final individual showdown in Saturday’s final.

Between them, Titmus (200m & 400m) and Ledecky (1500m) have dominated the freestyle titles after living up to their billing as headline acts in this week’s swimming action in Tokyo.

And as they look to add an 800m gold medal to their growing legacies, Ledecky claimed the psychological advantage by swimming the fastest heat time in 8.15.67, with Titmus qualifying sixth-fastest in 8.18.99.

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After her heat, Titmus conceded the hectic schedule was taking its toll. The Tasmanian spent another day backing up from the morning’s finals to the evening’s heats after helping lead Australia’s 4x200m freestyle relay team to bronze earlier in the day.

“I had an hour-and-a-half in my room today. I’m absolutely buggered,” Titmus said.

“This is probably my toughest back-up, and it’s not an easy 800 - this is a really deep field.

“So I knew I had to be tough and swim well to get through.

“Honestly, I’m bloody exhausted.”

Fellow Aussie Kiah Melverton produced a strong swim alongside Titmus in the third heat to also progress to the final.

Star backstroke duo Kaylee McKeown and Emily Seebohm cruised through to the semi-finals of the 200m backstroke, with the fastest and eighth-fastest times respectively.

McKeown will be looking to combine her 100m backstroke gold medal from earlier in the week with another success in Saturday’s final.

“It took a few days to relax and get the mindset back on track,” she said.

“I’m still feeling it a bit, so I’m just happy to get through to the semi-final.”

Australia’s Matthew Temple was eighth-fastest in going through to the semi-final round in the men’s 100m butterfly, but David Morgan was unable to get past the qualifiers.

Australia’s team of Isaac Cooper, Zac Stubblety-Cook, Brianna Throssell and Bronte Campbell qualified for the final of the inaugural mixed 4x100m medley relay with the fourth-fastest qualifying time.