The clash between Peeping Fawn and Alexandrova in the Darley Yorkshire Oaks on Wednesday looks in doubt.
Both fillies are trained by Ballydoyle maestro Aidan O’Brien and have already won three Group Ones apiece.
Peeping Fawn is on the crest of a wave following victories in the Pretty Polly, Irish Oaks and Nassau Stakes, but Alexandrova, who won last year’s race, has not been seen since last October.
O’Brien told www.racingpost.co.uk: “We discovered that Alexandrova was a bit tight behind when she came in from exercise this morning. We will see how she is tomorrow but there has to be a serious doubt about her running.”
The promising Silkwood, a five-length winner of Royal Ascot’s Ribblesdale Stakes, has been declared, as has Goodwood Cup heroine Allegretto.
However, connections have reported the former will only run if the ground is suitable.
Trick Or Treat and Under The Rainbow both run, while Dalvina and Darrfonah also take their chance in the 12-furlong contest.