Top jockey Ryan Moore will be sidelined for more than a month after suffering a neck injury on Thursday.
The 31-year-old was hurt at Newmarket's July Festival when his horse Newton's Law became trapped in the stalls.
Moore, who rode a record nine winners at Royal Ascot last month, is awaiting the results of a MRI scan.
His trainer father Gary said: "He's fairly comfortable, but he will be out for a while. He will be out for more than a month."
Earlier this year, Moore was appointed to the role as number one jockey to leading Irish trainer Aidan O'Brien.
Newton's Law was uninjured in the Newmarket incident, which happened ahead of Thursday's final race.
Moore, a three-time flat racing champion jockey, is leading this season's jockey standings.