Paris -Vasil Kiryienka, the veteran Belarus cyclist who helped Chris Froome to multiple Tour de France wins, retired on Thursday due to a heart issue.
"It's a really sad day for me, but it's the right decision based on the advice I've been given by the medical team," he said.
The 38-year-old rode in 20 Grand Tours - including alongside four-time Tour de France winner Froome - claimed a 2013 Vuelta a Espana stage victory as well as three Giro d'Italia stage wins, including a famous solo victory to Sestriere in 2011.
Kiryienka also won the individual time trial at the World Championships in 2015
Ineos team principal Dave Brailsford added: "It's disappointing for Kiry and for us as a team. He is a true one-off and one of the greatest team riders of his generation.
"When a rider in a breakaway looked back and saw the open shirted Kiry on the front of the peloton driving the chase they knew their days were numbered."
Fellow Ineos rider Geraint Thomas, the 2018 Tour de France winner, said he believed that Kiryienka would never retire.
"Long after I've stopped I thought he'd still be on the front of a peloton somewhere, ripping it to bits," tweeted the Welshman.
"A true one-off and one of the best teammates you could ever wish for We will miss him. Thanks for everything mate."