Buveur D'Air will not bid for back-to-back victories in Thursday's Betway Aintree Hurdle due to an unsatisfactory trachea wash.
Trainer Nicky Henderson has scratched the dual Champion Hurdle winner from the Grade One over two and a half miles.
"His trachea wash was just not very clever. He's got a bit of mucus and it's messy in there. It's not right, so it's not fair to run him if it's not," said the Seven Barrows handler.
Henderson explained the situation in full on his Twitter feed with the following statement: "Sadly, Buveur D'Air will not run at Aintree on Thursday due to an unsatisfactory trachea wash. It is a very routine procedure, and something we do with all of our runners, but he was found to have a small amount of mucus which means unfortunately we just cannot run him.
"It is terribly frustrating, but the horse's welfare is of paramount importance and it tells us he is not 100%.
"His work has been great, but you can never tell until you take these trachea washes and it is telling us that it would be unwise to run him.
"I have spoken to JP (McManus, owner) and it is extremely disappointing as this race had very much the plan ever since his win in the Unibet Champion Hurdle and he had ideal ground conditions too, so this is a bitter blow.
"There is the option of Punchestown (Betdaq Champion Hurdle on April 27) and we will think about it, but at the moment our main priority is getting Buveur back to full health."
Buveur D'Air took his winning run to 10 when holding Melon by a neck in a thrilling finish at Cheltenham last month.