Melbourne Cup contender Riff Rocket has died almost a week after undergoing an emergency operation.

The Chris Waller-trained horse was rushed in for colic surgery just days before he was due to launch his campaign at Flemington.

Initial signs of a recovery were positive but fears that the four-year-old champion would not make it were realised on Tuesday.

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“It is with deep sadness that we announce the passing of Riff Rocket following complications arising from his colic surgery,” Waller said in a statement.

“This is an incredibly difficult time for everyone involved, as we mourn the loss of not just a magnificent racehorse but also an extraordinary animal who made an indelible impact on Australian racing.”

Waller said the “complexities often associated with such (bowel) surgeries persisted”.

“Despite round-the-clock efforts from veterinarians and caregivers over the past seven days, we were unable to overcome these challenges,” he wrote.

Riff Rocket won $3.5 million in prize money with three Group 1 victories to his name — the Victoria Derby at Flemington last year, the Rosehill Guineas in March this year and the Australia Derby at Randwick two weeks later.

He is just the fourth horse to follow up a Victoria Derby triumph with victory in the next Australia Derby.

He also won the Group 3 CS Hayes Stakes and finished third in the Group 1 Australia Guineas, both at Flemington in February and March.

Riff Rocket was equal favourite for this year’s Caulfield Cup and a top contender for the Cox Plate as well as the Melbourne Cup.

“This is a heartbreaking loss not only for the Kepitis family but also for the entire team at Chris Waller Racing,” Waller said.

“Riff Rocket will forever hold a special place in our hearts, remembered for the fighting spirit he displayed both on the racetrack and in his final days.

“Our thoughts go out to all those who had the privilege of working with and supporting Riff Rocket throughout his career.

“He will be deeply missed, but his legacy will continue to inspire us all.”

Riff Rocket had opened his account for the new season with a second-place finish behind Via Sistina in the Winx Stakes at Randwick last month.

He fell ill just days after being dispatched to Melbourne alongside Via Sistina as one of Waller’s “three headline acts” for the Makybe Diva Stakes.