The victory at Liverpool came hard on the heels of United's unhappy exit from the Champions League at the hands of Bayern Munich on Wednesday and the weekend's Premier League defeat by Chelsea which pushed his team down to second in the table.
"I've had a lot of great winners, but to win a race of this magnitude and class is fantastic. I'm really pleased," local media quoted Ferguson as saying.
"It's great. That's the beauty of the racing game. Every fence you're jumping yourself, that's the beauty of it."
Referring to Wednesday's Champions League quarter-final loss, he said: "You have your disappointments and no one died last night. That's the important thing and you move on. Life is like that. Every day is a different day."
Ridden by Ruby Walsh for champion trainer Paul Nicholls, What A Friend (5-2 second favourite) took up the running after the last fence to score by three and a quarter lengths from Carruthers.
It was a fine victory but one made easier by the fall half way round the second circuit by last month's Cheltenham Gold Cup winner Imperial Commander, the 11-8 favourite.
Ridden by Paddy Brennan, Imperial Commander had upset the script for the Gold Cup which had been billed as the all-time showdown between former winners Kauto Star and Denman.
But on a different track and racing less than three weeks later Imperial Commander was clearly struggling on the second circuit and the fall was not a complete surprise.
Ferguson was on hand to witness What A Friend's success and was jumping up and down with joy in the winner's enclosure and slapping all his companions on the back.
"It's a young horse, next year we're going for the Gold Cup," a beaming Ferguson told Sky Sports News with a laugh.
Ferguson is no stranger to big-race success. He was a part owner of flat race champion Rock of Gibraltar who in 2001-2002 set a world record of seven consecutive Group One victories.
Thursday's race was the highlight of the first day of the big Grand National meeting.
Among the 40 runners for Saturday's eagerly anticipated event are Mon Mome, 100-1 winner last year, and 2008 hero Comply or Die.
