The 2016 Cheltenham Gold Cup winner Don Cossack has been retired due to injury.
The Gordon Elliott-trained 10-year-old suffered a recurrence of a tendon injury and will be sent to stud.
Don Cossack won the Gold Cup under Bryan Cooper 10 months ago and that famous victory will be the gelding's last race.
Elliott revealed in his Betfair blog: "We found that he had a bit of heat in his leg yesterday [Tuesday] and we've made the decision to call time.
"It's a real sickener for Gigginstown [his owners], myself, Bryan Cooper and the whole yard.
"We knew it was never certain we would get him back to the racecourse - and even after that to get him back to his best - but we were hopeful and he was on track for a run at Gowran Park next month.
"He's a horse of a lifetime and he owes us nothing. I said all season that if he had any sort of setback at all we would not abuse him and retire him straight away."
The 2015 winner Coneygree will also be absent for the Gold Cup in March, with Thistlecrack an odds-on favourite for the blue riband event at the Cheltenham Festival.