The identity of Aidan O'Brien's Epsom Derby runner is unlikely to be definitely known until the horse boards the plane to England tomorrow morning, but O'Brien was more hopeful yesterday that Saffron Walden will be the one to travel.

There are still major concerns about the ground for the Irish 2,000 Guineas winner, but with only showers falling at Epsom yesterday, Saffron Walden's chances look to be improving.

"I hear the going is still good to soft, so I have to be hopeful. If the weather doesn't go the wrong way now, there must be a big chance Saffron Walden will run," O'Brien said yesterday.

Tchaikovsky is on standby to switch with Saffron Walden from the French Derby on Sunday.

"One horse will travel to Epsom on Saturday morning and one will run in the French race. We will leave a decision for as long as possible," O'Brien added.