Cameron McEvoy expects a "very fast" men's 100m freestyle final at the world championships on Thursday with a "dog-fight" on the cards and the blue riband event wide open.
France's Mehdy Metella clocked the fastest time from Wednesday's semi-finals of 47.65 seconds, but all of the top five swam under 48 secs.
With both Olympic gold medallist Kyle Chalmers and China's world champion Ning Zetao missing in Budapest, the 100m title is up for grabs.
Australia's McEvoy, 23, the world silver medallist two years ago in Kazan, was fourth fastest at just 0.30 secs behind the Frenchman.
United States sprinters Nathan Adrian and Caeleb Dressel, plus McEvoy and 18-year-old Jack Cartwright of Australia, joined Metella in going under the 48-seconds mark in the semis.
"The top five guys have all sneaked under 48 — usually you're lucky to get that in a final. Relative to 2015 only me and the winner went under that," said McEvoy.
"It's exciting, it's all about soaking it up on the night, historically anyone can do it.
"There's always at least someone unexpected who is in the top three. I think it's going to be very fast."
Britain's Duncan Scott clocked 48.10, just 0.48secs behind the Frenchman and has a chance of a medal.
"Bring on the dogfight, there's going to be fast times all over the shop," said the 20-year-old Scotsman.
"It might take a personal best just to get a medal or even reach the top five."
Ahead of the men's 200m individual medley final, Chase Kalisz of the USA was the fastest qualifier at 1:55.88 with Japan's Kosuke Hagino, the Olympic 400m individual medley champ, just behind.
His compatriot Daiya Seto, the 400m IM world champion was fifth fastest.
"It felt good, I'm excited for the final," said Kalisz, the 400m IM silver medallist at last year's Olympics.
China's Fu Yuanhui was second quickest into the women's 50m backstroke final behind Brazil's Etiene Medeiros, who clocked 27.18secs — just 0.12 short of the world-record.
Emily Seebohm, who won bronze when Canada's Kylie Masse broke the women's world record in the 100m backstroke final on Tuesday, and Australia team-mate Holly Barratt were joint fifth fastest as both swam 27.51.
"I was really happy with that, it's pretty close to my best, but I know I did an average start again, so I'm looking forward to hopefully getting everything right," said Seebohm.
Germany's Franziska Hentke was the fastest into the women's 200m butterfly final after clocking 2:06.29, but China's Yilin Zhou was just 0.34 behind her.
Following her 200m individual medley gold medal on Monday, home-crowd favourite Katinka Hosszu was the sixth fastest and says fatigue is not an issue despite having raced every day so far at these championships.
"I don't feel exhausted really, I have some reserves left although I have swum quite a lot already. The final tomorrow will tell how much I can take," said Hungary's 'Iron Lady'.