The hugely popular Red Cadeaux has run his last race without being able to finally shed his Melbourne Cup bridesmaid's tag.

The three-time Cup runner-up failed to finish in his fifth Cup attempt in as many years, suffering a fracture in his left leg.

Vets say Red Cadeaux's injury is not currently life threatening but he has been immediately retired by English trainer Ed Dunlop.

Dunlop had feared the 10-year-old, a crowd favourite at home and abroad, would have to be put down.

"When I was on the grass, I thought we wouldn't see him alive again," Dunlop told reporters.

"He's alive and well.

"He's eating grass. He looks happy, He has fluids. It's a bad injury, but it should be repairable."

It had been expected that Dunlop may announce Red Cadeaux's retirement after Tuesday's Melbourne Cup, but not in this way.

"We've discussed three or four times we were going to retire him and we haven't retired him," Dunlop said.

"All seemed very well with him but unfortunately it wasn't to be.

"I thought he was going to be put down."

Red Cadeaux suffered a fracture in his left fore fetlock and was stabilised on course before being taken to the University of Melbourne Equine Centre in Werribee.

The horse is comfortable with his leg in a splint and the fracture is stable, Racing Victoria vets said.

University of Melbourne vet Dr Chris Whitton said the injury is not currently life threatening but Red Cadeaux will not race again.

The vets are talking to other world-leading equine orthopaedic surgeons to come up with a plan to repair the injury.

Dr Whitton said Red Cadeaux will not undergo surgery on Tuesday, given the horse is comfortable, and several options are being considered to treat him.

Dunlop said he and Red Cadeaux's connections will do everything in their power to ensure the horse makes a full recovery.

"If the guys do their job, he'll have a very happy retirement."

The popular British stayer is only the third horse in Cup history to run the race five times in a row.

Red Cadeaux has made the long trip out to Australia six times. Earlier this year he came to Sydney where he ran second to Criterion in the $4 million Queen Elizabeth Stakes.

The Australian public has practically adopted the horse, who loves his time here.

"He seems to become a different horse around here," Dunlop said on Sunday.

The injury to Red Cadeaux was a sad postscript to a history-making Melbourne Cup in which Michelle Payne became the first female jockey to win the race on outsider Prince Of Penzance.

It follows the deaths of Admire Rakti and Araldo after last year's Melbourne Cup and in 2013 Verema was euthanased after breaking its leg during the race.