Get The Idea is the outsider in the Rosehill Guineas but his trainer John Sargent thinks highly enough of the lightly raced three-year-old to test him in the Group One race.

Get The Idea heads into Saturday's 2000m feature for three-year-olds at Rosehill off three provincial races.

He won a 1300m-maiden at Kembla Grange and a class one over 1500m at Newcastle before finishing second in a class two at Newcastle over 1600m as the odds-on favourite.

His Rosehill Guineas rivals include dual Group One winner Shadow Hero, Cox Plate runner-up Castelvecchio, Victoria Derby winner Warning and New Zealand Derby winner Sherwood Forest and his performance will determine whether he goes to the Australian Derby (2400m) at Randwick.

Sargent scratched Get The Idea from a 2000m benchmark-64 at Hawkesbury on Tuesday to give him his chance in the Guineas.

"He's a nice progressive horse and will probably be better in six months time but they are only three once so he's having a go," Sargent said.

"If he goes well he will go on to the Derby.

"He's got all the ability in the world, he's probably just got to strengthen a bit.

"Saturday will tell us where we are in the mix against Shadow Hero and those good stayers. If he can run close and be right there we'll press on to the Derby. If not we won't.

"He's bred to get up over ground so I don't think a mile and a half would worry him."

To be ridden by Rachel King, Get The Idea, by So You Think out of Cavita, is raced by the Think Big syndicate started by the late Dato Tan Chin Nam and races in his famous colours.

He was at $101 on Wednesday with Shadow Hero, winner of the Group One Randwick Guineas at his most recent start, the $3.70 favourite.

Although Get The Idea did a few things wrong last start, the trainer believes he has the raw talent to be competitive.

"He should have won all his starts," Sargent said.

"He ran off the track last start and we've ironed a few things out with him. He seems to be galloping good and true, so I'm very happy with him."

The Rosehill Guineas is the second leg of the Sydney autumn three-year-old triple crown with the Randwick Guineas the first and the Australian Derby the third.