Imported Japanese horse Admire Deus has undergone surgery after suffering a life-threatening leg injury in the lead-up to the Caulfield Cup.

Admire Deus was the one-time Caulfield Cup favourite but broke down during trackwork at Warrnambool eight days ago, hours before acceptances for last Saturday's $3 million Caulfield Cup were taken.

The seven-year-old, who was bought by Australian Bloodstock and sent to Darren Weir to be trained for the Caulfield and Melbourne Cups, underwent more than 4-1/2 hours of surgery on Tuesday.

Weir says the surgery went well but the next six to eight weeks will be crucial as Admire Deus fights off possible infection, laminitis and implant failure.

Weir received a pleasing follow-up report from surgeons on Wednesday.

"This morning he wasn't as bright as normal but it's less than 24 hours after anaesthesia," Weir said.

"He's had two small feeds and passed manure and the plan is to put him on fluids for 24 hours."