Aintree Grand National winner One For Arthur has been ruled out for the season, trainer Lucinda Russell confirmed.
This year's Aintree hero is suffering with a tendon problem in his right fore and will not attempt to repeat his famous Grand National success next April.
Russell said: "He's out for the season. It's not a big injury, but it's enough for us to stop with him.
"It's obviously a shame, but hopefully we can get him back to full fitness."
Russell added the injury was discovered on Wednesday when One For Arthur had undergone a first piece of work since his summer holidays.
He was found to have disrupted fibres in his "right fore superficial flexor tendon".
The eight-year-old gelding was one of the most evocative winners of the Grand National in recent times as he defeated Cause Of Causes by four and a half lengths under Derek Fox.
Stabled in Kinross, Tayside, One For Arthur became the first Scottish-trained winner of the big race since Rubstic in 1979.
He was also the ante-post favourite to repeat the feat next spring.
