William Buick will partner Romsdal in the Ladbrokes St Leger at Doncaster at Saturday.
Buick, who will be seeking his third victory in the Classic, had the choice of Romsdal and Forever Now, who are both trained by his boss, John Gosden.
Romsdal finished third in the Derby and was last seen when well beaten in the King George at Ascot, while Forever Now won the March Stakes at Goodwood on his latest outing.
Despite that victory, Buick has decided to partner the former.
He told his At The Races blog: "I'll always have a soft spot for the Ladbrokes St Leger because it was the race in which I rode my first British Group One - and Classic - with Arctic Cosmos back in 2010.
"I won it again in 2011 with Masked Marvel and after shuffling the cards for 2014, I've decided that if I'm going to get a third on Saturday then it's going to be with Romsdal.
"On the face of it the decision might have looked easy with Forever Now rated 106 and Romsdal 9lb higher, but the fact is that I've only ridden Romsdal once in his five starts this season whereas I've been with Forever Now on all five outings, winning twice.
"He's got plenty of courage and stays very well, but in the end I just gave the nod to Romsdal on having the better overall level of form and that when I did ride him we were only beaten a nose by Orchestra in the Chester Vase over 12 (furlongs), staying on strongly.
"I've made my decision - I think it's the right one so here's hoping."
Frankie Dettori has been confirmed as the rider of Forever Now.
It has been a difficult week Dettori after Thierry Jarney regained the ride on last year's Prix de l'Arc de Triomphe heroine Treve at the popular Italian’s expense.
Dettori's agent Ray Cochrane said: "Frankie will ride the John Gosden horse (Forever Now) in the St Leger, which is great.
"It's not all doom and gloom.
"Last month Frankie rode a Group One winner in France for James Fanshawe (Ribbons) and I'm sure Hayley Turner (previous jockey) wasn't too pleased, but that's the way it goes.
"It's swings and roundabouts."
ne so here's hoping."
