Simonsig put down after broken leg at Cheltenham
The Nicky Henderson-trained Simonsig was put down after he broke a leg during the Shloer Chase at Cheltenham on Sunday.
The 10-year-old grey sustained the injury when he fell at the third fence.
"You all know what the game is like. It tests us, and it is one of those things," said Henderson.
It happened on the same day the Henderson-trained Sprinter Sacre - winner of nine Group One races - was retired after a tendon injury.
Simonsig won eight races from 13 starts, including the Neptune Novices' Hurdle at the Cheltenham Festival in March 2012 and the Arkle Trophy a year later.
The gelding had struggled with injury since that victory and only returned to the track at Aintree in November 2015, after which he only raced three more times.
Subscribe to the BBC Sport newsletter to get our pick of news, features and video sent to your inbox.