This year’s Aintree hero is suffering with a tendon problem in his right fore and will not attempt to repeat his famous Aintree success next April.
Milnathort-based 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 that the injury was discovered on Wednesday when One For Arthur was undergoing 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, becoming 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.
In today’s action at Ascot, Ekhtiyaar, who has been a quietly progressive sprinter this year, is expected to do the business.
Roger Varian’s colt has won two nice races this season and already looks capable of running at a higher grade. For now, though, connections have decided to stick to handicaps, with the decision likely to be vindicated in Berkshire.
Ekhtiyaar will need a touch of fortune on his side as 13 other horses have been declared for this six-furlong dash.
But he showed on his last outing at Newmarket in July, when he gamely defeated Tommy Taylor by a head, that he thrives under the restraints of big-field handicaps.
The son of Bated Breath has gone up 6lb for this assignment, yet that should not necessarily be too much of a hindrance as he is seemingly still on the march.
Ekhtiyaar has won when there is cut in the ground, too, so that could be of importance.
Owner Hamdan Al Maktoum can also welcome another winner later on the card when Mukalal goes for a seven-furlong handicap.
The three-year-old gelding, trained by Marcus Tregoning, has made hay on the all-weather this year but he is certainly no slouch on the turf, either.