Irish trainer Aidan O'Brien has revealed the 2,000 Guineas second favourite Kingsbarns is a doubt for the Classic at Newmarket on 4 May.
Kingsbarns, the Racing Post Trophy winner and around a 6-1 shot for the one-mile contest, has a foot infection and missed 10 days of work, including a workout at the Curragh on Sunday.
"You'd have to be worried about him for the Guineas," admitted O'Brien.
Dawn Approach, trained by Jim Bolger, is the 2-1 Guineas favourite.
Bolger enjoyed a successful first day of the Irish season with four winners: Saburo, Caesaria, Rehn's Nest and Derby entry Alpinist.
The County Kilkenny-based trainer won the 2008 Derby with New Approach.