The future is uncertain for Coneygree, trainer Mark Bradstock indicating he could be given a wind operation after he was pulled up in the Ladbrokes Trophy at Newbury on Saturday.
The 2015 Cheltenham Gold Cup winner jumped well at the front off top weight under Nico de Boinville but weakened after a mistake on the back straight on the final circuit.
The ten-year-old had been backed in to 8-1 before the off in the £250,000 contest won by Total Recall but the outcome was a second successive failure to complete after the Charlie Hall Chase last month.
Bradstock reported: “Nico said he made a noise. We'll probably send him to Bristol to have a look to see what we can find out.
“He’s been a superstar and owes us absolutely nothing. We thought we had him absolutely on song and he jumped superbly. But that’s the way it goes. It’s back to the drawing board.”
American, the 5-1 second favourite, was another to disappoint, being pulled up four fences from home. Jockey Noel Fehily said: "He made too many mistakes. His lack of experience told."