American superstar Katie Ledecky had made a big statement in pipping Ariarne Titmus in their blockbuster 400m freestyle heat on the opening day at the Olympics.
Titmus, who won the event in Tokyo, looked on track for a dominant victory, but Ledecky came from behind to steal the victory in the final 50m.
It means the Aussie world record holder and five-time gold medallist will swim from lane five in Sunday morning’s final.
Know the news with the 7NEWS app: Download today 
“Just having a look at Arnie at the end of that race, she actually didn’t look that pushed,” Giaan Rooney said on Nine’s coverage.
“It didn’t look comfortable in that last 100 (metres) but I also wonder if that was a bit of a play of ‘I don’t want to burn everything I have this morning, if you want to post that time you post that time, I don’t need to’.”
There will be another Australian in the final with Jamie Perkins qualifying fifth fastest.
Kiwi Erika Fairweather (third) and Canadian Summer McIntosh (fourth) both swam well to set the scene for the epic final.
McKeon makes hot start
Aussie superstar Emma McKeon booked her spot in the semi-finals of the 100m butterfly after a strong performance in her heat.
McKeon swam in the second of four heats and finished second in a time of 56.79, just behind China’s Zhang Yufei (56.50).
“Not a great touch on the wall either from Emma,” Ian Thorpe said on Channel 9
“Had a bit of a long glide. So improvement to come in.
“She did what she needed to do and we are away.”
Fellow Aussie Alex Perkins stormed home to finish third in her heat in a time of 57.46, which was enough to secure a spot in the top 16 times.
McKeon qualified fifth-fastest overall, while Perkins was eighth.
The semi-finals will be on Sunday morning (AEST).
More to come …