Colin Tizzard hopes to have Thistlecrack back on a racecourse around Christmas time after a season-ending tendon injury saw him become the latest high-profile name to be ruled out of next month's Cheltenham Festival.
The dominant force in the staying hurdle division last year, the nine-year-old won his first four starts over fences, including a scintillating victory in the King George VI Chase at Kempton on Boxing Day. He was favourite for the Cheltenham Gold Cup on March 17.
Tizzard said: "Thistlecrack is out for the season, unfortunately.
"He had a bit of heat in his leg and was a bit sore. We had the leg scanned and he has a slight tear on his tendon. We know it's not very serious, that's racing, that's horses for you."
The news comes as another huge blow to National Hunt's showpiece meeting, which starts on March 14, with Thistlecrack joining the likes of Coneygree, Annie Power and Faugheen on the sidelines.
Native River is the new 5-2 Gold Cup favourite.