Ladbrokes Trophy ante-post favourite Topofthegame has been ruled out for the season by trainer Paul Nicholls.
The 9-2 shot for Newbury's big handicap on November 28 had a recurrence of the tendon injury which has kept him on the sidelines since 2019.
In a statement on his website, Nicholls said: "I'm sorry to report that Topofthegame is out for the season.
"I was hopeful of a big show from him in the Ladbrokes Trophy at Newbury at the end of the month.
"But all plans are on hold because the tendon injury he suffered last winter is again giving me cause for concern."
Topofthegame won the 2019 RSA Insurance Novices' Chase at the Cheltenham Festival, form that was advertised at the top level last season by placed horses Santini and Delta Work.
The following month, the eight-year-old chased home subsequent Magners Gold Cup third Lostintranslation in the Betway Mildmay Novices' Chase at Aintree.
He has not raced since and Nicholls added: "The warning signs have been flashing over the past few days and the decision to draw stumps was taken this morning after discussions with his owners Paul Barber and Chris Giles.
"Scans taken by our vet showed that the original tendon damage is still a little weak.
"It is the right thing to stop now."
The Colin Tizzard-trained Copperhead is now the 8-1 favourite with the Ladbrokes Trophy sponsors.
Spokesman Jon Lees said: “Topofthegame’s challenge for the Ladbrokes Trophy under top weight was already drawing comparison with race legend Denman so his absence from the race is a real disappointment.
"As a result we now have Copperhead, whose stable has won the race twice in the last four years, as favourite and have shortened others behind him, including last year’s first and second De Rasher Counter and The Conditional.”
