Tulloch Lodge trainer Gai Waterhouse has backed the decision of her stable's No.1 jockey Tommy Berry to ride at the George Ryder Stakes meeting at Rosehill.

Berry has been at the bedside of twin brother and fellow jockey Nathan who has been in a Singapore hospital since he collapsed at Kranji trackwork last week.

Nathan has been diagnosed with NORSE syndrome and placed in an induced coma.

Waterhouse said she had been in contact with her jockey and supported his move to ride on Saturday.

"Absolutely. He can't do any more and Nathan would have told him to do the same thing," Waterhouse said.

"It's a terrible situation for the family, for Tom, most of all for Nathan's young wife. It's the saddest thing you can possibly imagine.

"I've texted him and I said don't you worry about me, you just get on and look after your brother."

Tommy Berry and Nathan's father-in-law Glyn Schofield both missed last weekend's Coolmore Classic meeting to be with family in Singapore.

But they have confirmed they will return to ride at Rosehill on Saturday before heading back to be with Nathan.

Berry has a full book of nine rides, all trained by Waterhouse.

Among them is Order Of The Sun who runs in the Group One Rosehill Guineas.

A Randwick winner over 1600 metres two starts ago, the colt was down the track against older horses in the Chipping Norton Stakes but he did finish within five lengths of winner Boban.

As a son of Encosta De Lago, Waterhouse is counting on the step up to 2000 metres to suit the colt.

"If they can stay it's half the battle," Waterhouse said.

"He's a lovely horse and all along I've said he's my Derby horse."

Randwick Guineas winner Dissident has opened favourite for the Guineas at $4.60 ahead of New Zealand Derby winner Puccini ($4.80) and Shamus Award at $7.

Order Of The Sun is a $26 chance.