Trainer Darren Weir says the next 72 hours are crucial for Admire Deus who is being treated at a veterinary clinic for a serious leg injury suffered in a track gallop at Warrnambool.

Admire Deus had shortened into favouritism for Saturday's Caulfield Cup on Monday night, but less than 12 hours later his spring carnival was over.

Weir said after doing his last main gallop at Caulfield on Saturday, the Japanese import was out stretching his legs on Tuesday morning when he suffered the injury.

"It's just shocking luck what has happened but you wouldn't change any of his work along the way," Weir said.

"The horse was just having a stride along. He had his hard gallop here (Caulfield) on Saturday.

"He was just stretching his legs this morning and unfortunately it's happened.

Weir said the horse was taken to the Ballarat Clinic where scans confirmed he had severely damaged a suspensory lligament.

"The next 72 hours is crucial to see what happens," Weir said.

After being bought by Australian Bloodstock, Admire Deus was brought to Australia to be trained by Weir.

AB director Jamie Lovett tweeted his disappointment.

"Devastated for Admire Deus,Matt Scown, Shiny @shiny_7592, Craig Williams, Darren Weir and all connections" Lovett said.

Weir will have two runners in Saturday's Group One handicap with Humidor drawing barrier seven and Amelie's Star gate 13.

With the injury to Admire Deus, his jockey Craig Williams now has the ride on Amelie's Star, replacing Michael Dee.

Weir said the booking of Williams over Dee had been blown out of proportion.

He said Dee was only booked for the ride on Monday night and he was not sacked.

"He didn't have the ride for six weeks and he didn't get off anything else to ride the horse," Weir said.

"He also had never ridden the horse before.

"The owner was happy with Micky Dee but when Craig Williams became available he thought it was in his best interests as Craig's had more experience."

Racing Victoria stewards have spoken with Dee who said he would not ask for a losing fee or any prize money.