It has been confirmed that Sire De Grugy will not race at Cheltenham Racecourse this weekend as planned.
This year's Queen Mother Champion Chase winner had been due to appear in the Shloer Chase, but following a routine workout earlier today, the eight-year-old was found "lame".
"He's not going to run on Sunday, unfortunately. He worked well this morning and was fine straight after, but he's lame now," said trainer Gary Moore.
The news has resulted in speculation that the chestnut gelding could also miss the defence of his Tingle Creek title in December, although Moore is hopeful that he can compete at Sandown.
"I'm hoping he'll be OK for Sandown, but it's up in the air. There's nothing obvious, but he is lame," added Moore.
Sire De Grugy has won 14 of his 25 races during his career.