Jockey Trevor Whelan suffered a unlucky break at Chester on Saturday.
The rider won the ESL Group Novice Stakes aboard 10-1 chance Rockesbury for trainer David Loughnane, but was unshipped after the line.
He was taken for further examination, which revealed he had fractured his ankle.
Whelan tweeted: “Fractured ankle @ChesterRaces after winning the race least it won.”
Better known in the National Hunt world, Whelan has been busy on the Flat during the summer and won the Listed 32Red Stand Cup at Haydock in September on the Roger Charlton-trained Blakeney Point
His headline successes over jumps have come with the Neil King Lil Rockerfeller, on whom he went within three-quarters of a length of winning the World Hurdle at the Cheltenham Festival in 2017.