New Zealand cyclist Greg Henderson is facing legal action after accusing Fabio Aru of feigning illness to cover up issues with his biological passport.
The Italian rider missed the Giro del Trentino with a stomach ailment, which prompted Henderson, who rides for the Belgian Lotto-Soudal road racing team, to question his sickness and label him a cheat.
"Sad to see @fabaro1 'sick'. Mate make sure next time u come back to our sport 'healthy'. Aka Clean! #biopassport! Or don't come back!" Henderson wrote on Twitter.
Henderson, who won gold for New Zealand on the track at the 2002 Commonwealth Games, followed it up with another tweet. "I am so sick of it. It becomes common knowledge within days. Why try cheat."
He quickly removed the Twitter posts, before issuing an apology the next morning.
"When you are sick. You are sick. Jumping to conclusions helps nobody. My mistake @FabioAru1. I should shut my mouth. Sincere apologies."