Cheltenham Gold Cup favourite Thistlecrack will miss the remainder of the campaign after suffering a tendon injury.
The dominant force in the staying hurdle division last season, the Colin Tizzard-trained 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.
Despite suffering a narrow defeat at the hands of the ill-fated Many Clouds in the Cotswold Chase at Cheltenham at the end of January, he remained at the head of the betting for the blue riband on March 17, but he will not line up at Prestbury Park next month.
Tizzard said: "Thistlecrack is out for the season, unfortunately. He had a bit of heat in his leg last night and was a bit sore.
"We had the leg scanned this morning and he has a slight tear on his tendon.
"We've seen it at every yard and it happens every year."
Despite the shock news, Tizzard still has a formidable hand for the Festival showpiece.
Paddy Power make Thistlecrack's Hennessy Gold Cup, Welsh Grand National and Denman Chase-winning stable companion Native River the new 5-2 favourite, just ahead of fellow Venn Farm inmate Cue Card at 3-1.