Ariarne Titmus called Summer McIntosh "an absolute phenomenon" on Monday after the Canadian smashed her 400m freestyle world record, with the Australian star admitting it had got her "juices flowing" again.
The 18-year-old hit the wall in 3min 54.18sec at the Canadian world championship trials over the weekend, demolishing Olympic champion Titmus's 3:55.38.
"Obviously, it stings a little bit when you get your world record broken," said Titmus, who is taking a season off before she dives back in to prepare for the 2028 Los Angeles Games.
"But I know how tough it is to swim that fast. To break my world records, I was working for years and years.
"And to be 18 years old and to be swimming that incredibly off the back of the Olympic Games, she's an absolute phenomenon. To smash the world record like that, who knows how far she's going to go," she said.
But Titmus, who won 400m gold at the Tokyo and Paris Olympics and owns three of the five fastest times in history, stressed it was good for the sport.
"This is great for the world of swimming. We want to keep seeing more and more women be fast and create rivalries," she said at the Australian trials in Adelaide, where she is on commentary duty.
"And you know, I was the first person to beat (American) Kate Ledecky (over 400m), and now Summer's taking it to us, and I think it's great for our sport."
Asked if losing her world record was a motivator to get back in the pool, Titmus replied: "It gets the juices flowing."
Titmus remains the 200m freestyle world record holder.