Aidan O'Brien's Age Of Aquarius may have to be retired from racing after he suffered a bad leg injury at Goodwood yesterday.
O'Brien's stayer broke down with around half a mile to run of the Artemis Goodwood Cup, for which he was sent off the odds-on favourite.
The four-year-old was loaded into a horse ambulance and taken away to Arundel Veterinary Practice for further examination, where X-rays revealed he had suffered ruptured ligaments in his off fore.
Dr Paul Dupreez, senior partner of the Arundel Equine Hospital, said: "He is fine and is on his way home, supported by a splint and bandages.
"It is not a catastrophic injury, but there are huge doubts as to whether he will be able to get back to competitive action. He's a very valuable horse and I'm sure they will have plans for him."
Jockey Johnny Murtagh was leading the field, but soon pulled up his partner once the Galileo colt had lost his action.
Murtagh said: "He was travelling OK, but lost his balance for a couple of strides and it went pop. It was disappointing as he was going well."
Age Of Aquarius was backed into 4-6 favouritism for the Goodwood Cup, won by Illustrious Blue, who thrust local trainer William Knight into the spotlight with his victory.
Knight is based just 15 miles across the rolling Downs from the track and basked in the glory as Jim Crowley brought the 8-1 chance home a length and a quarter clear of Electrolyser.
Illustrious Blue was anchored in the rear for much of the journey and only started to attack on the five-furlong dash to the line.
Electrolyser had been left at the head of affairs when the favourite broke down, and it took a huge effort for Knight's seven-year-old to wear down the grey.
The winner had shed his maiden tag at Goodwood way back in the early part of 2006 and was registering his third win at the Glorious meeting.
Knight, in just his fifth year with a licence, said: "There is not a lot I can say but I am very, very happy.
"I said to my wife with four furlongs to run that I thought we would win and I wouldn't usually do that.
"This is my local track and he has now won at Glorious Goodwood three times so you can't ask for more.
"We'll sit back and look at the options now, but there is the Lonsdale at York and the Doncaster Cup to consider, and we are also thinking about a trip to Melbourne."
Crowley added: "You could not wish for a nicer character of a horse. He is a legend and has not run a bad race all year.
"I think he could be an Ascot Gold Cup horse next year as he stays well enough."
Electrolyser had raced just once previously this season, when third to Illustrious Blue in the Sagaro, and could head abroad next time out.
Trainer Clive Cox said: "I'm really pleased because he has proved as good as I thought he was."
International campaigner Purple Moon had taken third in the Gold Cup and put in another solid effort to occupy the same place.
Nicky Henderson's 13-year-old Caracciola, who has wins over hurdles and fences in addition to the 2008 Cesarewitch to his name, finished back in eighth place on what was his final racecourse appearance.