One of Buckaroo’s half-brothers will be a rival in his quest for another Underwood Stakes

Buckaroo is aiming to defend his Underwood Stakes crown off a different lead-up against a new set of rivals, but one in particular offers similarity of sorts.

The Chris Waller-trained son of Fastnet Rock will do battle with half-brother, Roaring Lion gelding Middle Earth, in the $1 million Group 1.

That Ciaron Maher-trained import, like Buckaroo, is out of the Galileo mare Roheryn.

The Underwood Stakes will be their second clash, but their best hope of being in the finish after both finished outsiders in the Group 1 Queen Elizabeth Stakes earlier this year.

Both resumed at Caulfield on August 30, Buckaroo with a third placing in the Group 1 Memsie Stakes (1400m) and Middle Earth with a fifth placing the 2000m event won by last Saturday's The Archer winner Revelare.

Buckaroo won last year's Underwood Stakes off a Group 2 Chelmsford Stakes win, which followed a Winx Stakes eighth placing, and while Waller would have preferred he had an extra run under his belt he is happy with his condition for the stage of his preparation.

"His first-up run was excellent (and) you would expect the Memsie form to stand up," Waller said.

"I would have liked to have been third-up coming into the race, but instead of being third-up we've done the best we can – Memsie, he then had a trial at Flemington last Friday and he'll be ready to go Saturday."

Whether Buckaroo is forward enough to win will not be known until Saturday, but he appears well-placed to win the battle of the brothers with Maher expecting Middle Earth to come on from Saturday's race for targets over further later in the campaign.

"He's ticking along the right way," Maher said.

"He hit the line well and he'll strip fitter (but) the 1800 metres is probably short of his best."

The Underwood Stakes will be Middle Earth's first start below 2000m with his two Black Type wins and Group 2 Hardwicke Stakes third placing all coming at 2414m or beyond.

He and Buckaroo are the two Stakes winners from six to race from Roheryn, who was a Black Type winner herself and was a multiple placegetter at Group 2 and Group 3 level.

She is out of the More The Ready mare La Chunga, who has previously influenced racing in Australia with her final foal Fastnet Latina five-time winner in Australia after being exported by OTI Racing.