He started all five games as France regained the Six Nations in 2025, and was selected in their provisional squad for this year’s tournament.
However, he was withdrawn from the squad earlier this week. It is unclear whether that was for sporting or medical reasons.
“Uini is a wonderful person who really mattered both as a player and as a man within the group,” France’s forwards coach William Servat said on Wednesday.
“Our thoughts are with his family, his loved ones, his children, his wife – that’s what matters today.
“We’re all, of course, affected and saddened by what’s happening, but he’s a strong man, and we’re convinced that he’ll bounce back quickly.”
Having been spotted at a rugby 10s tournament in Hong Kong, Atonio signed for La Rochelle for the 2011-12 season and remained with the club for his entire career.
He helped his side win promotion to the Top 14 in 2014, and was part of a squad that reached three successive Champions Cup finals between 2021 and 2023, winning the title in the latter two years.
Atonio played six times this season, with his first appearance coming in early December and the last against Harlequins in the Champions Cup on 18 January.
“In Blue, just as in the La Rochelle jersey, Uini Atonio has been – and will remain – a great prop in the broadest sense of the term, in his stature, his humility and his sunny disposition,” the French clubs’ body the LNR said.
