Australian Paralympic champion Blake Cochrane always had his work cut out for him in defending his crown in Rio against Colombian teenager Carlos Serrano Zarate.
Serrano Zarate on Saturday stormed to his sixth world record in just over one year in the men's SB7 100m breaststroke, touching the wall six seconds before Cochrane, who was relegated to silver.
London gold medallist Cochrane said the 18-year-old, who burst onto the scene at last year's world championships, is up for review next year for classification.
The classification includes a number of different disabilities including those with amputations and cerebral palsy.
"And that's not my place to step in and engage in," Cochrane said on Saturday (Sunday AEST).
"I respect the (International Paralympic Committee's) decision. All I could do was go out there and swim my race, but I had to swim for second."
Cochrane said he had a similar rise to his arch-rival when first starting out in 2008.
"I came into Beijing. I was ranked, I think, second last and then I came in and did about a seven second (personal best) going into the final," he said.
The Queenslander said competing against such a lethal opponent pushes him to train harder.
"I wouldn't be in this sport if it wasn't for a good challenge," Cochrane said.
Another Australian medal in the pool came from 15-year-old Tiffany Thomas-Kane, who won her second bronze of the meet in the women's S6 50m freestyle in an Oceania record.
