Chris Waller on Tuesday paid tribute to his dual Derby winner Riff Rocket, who has died.

The four-year-old son of American Pharoah succumbed to complications from emergency colic surgery that was conducted early last week.

A shattered Waller fondly remembered the gelding, who was bred and raced by Debbie Kepitis and family, who last season joined Dulcify, Mahogany and Hitotsu as the only horses to complete the Victoria Derby/ATC Derby double.

“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.”

The last of Riff Rocket’s 12 starts came in the Group 1 Winx Stakes (1400m) at Randwick on August 24, when he finished seventh in the race won by stablemate Via Sistina.

It was his first start as a four-year-old, having stamped himself as one of Australia’s most exciting horses during a three-year-old season that netted six wins and three minor placings from nine starts.

After winning the Group 1 Victoria Derby last November, he returned in autumn to win the Group 3 CS Hayes Stakes and finish third in the Group 1 Australian Guineas become claiming the Group 1 Rosehill Guineas and Group 1 ATC Australian Derby during the Sydney carnival.

“Riff Rocket’s career as a three-year-old was nothing short of remarkable,” Waller said.

Riff Rocket was crowned last season’s New South Wales 3YO of the Year and was a leading contender for the national award, which will be announced in Adelaide early next month.