He first injured his groin in 2009 and in the 10 years since has never been able to fully heal it, citing the injury as one of the main reasons he switched from breaststroke to butterfly early in his career.
“I was never able to swim breaststroke again,” he said.
Doctors through the years were unable to pinpoint the exact issue.
The injury worsened in the weeks leading up to the world championships. After seeing a specialist in Qatar earlier this year, le Clos felt confident the problem had finally been properly diagnosed.
In the 200 fly, Le Clos lost to Hungary’s Kristof Milak, who broke Michael Phelps’ world record. In the 100 fly, le Clos lost to American Caeleb Dressel, who broke another of Phelps’ world marks.