Winning doubles to Chris Waller at Doomben and Randwick could not ease the pain of the loss of stable stalwart Rangirangdoo on Saturday.

The Waller-trained Zoustar won the Group Two Sires' Produce Stakes at Doomben and Hawkspur took out the Group Three Premier's Cup before Rangirangdoo broke down in the Doomben 10,000.

The dual Group One winner was euthanased after breaking both sesamoids mid-race.

Waller's Sydney staff waited anxiously at Randwick to hear what had happened and even victory by Coup Ay Tee in the final race to go with She's Clean's earlier win, couldn't lift their spirits.

"It is a tragedy," racing manager Liam Prior said.

"He has been a terrific horse to the stable, just a great horse.

"It's hard for it to end like this."

Nash Rawiller won the 2010 Doncaster on Rangirangdoo while Corey Brown was aboard in the 2011 George Ryder Stakes, his other Group One win.

Rangirangdoo won 10 of his 34 starts and more than $2.25 million prize money.