Five failures at beating top mare Silent Achiever aren't stopping Peter and Dawn Williams from sending Shuka out to try a sixth time.

Shuka is on the third line of betting for the Group One New Zealand Stakes (2000m) at Ellerslie, and success could earn him a crack at the Brisbane winter carnival.

But to win, the Karaka gelding will need to get past Silent Achiever, a warm favourite as she prepares for The BMW and the Sydney Cup.

Peter Williams rates Shuka as the better prospect for the race than his improving mare Etoile Filante, but says beating Silent Achiever after five previous defeats will be a tough task.

"Shuka has never beaten Silent Achiever, but he's run something like three placings to her," he told NZ Newswire.

"Whether he's improved enough to beat her we'll find out at Ellerslie."

Shuka comes into the race in good form, having won the Group One Captain Cook Stakes at Trentham in December and narrowly losing the International Stakes at Te Rapa to another of Saturday's rivals, Costume.

"He has a flat spot sometimes in his races and takes a wee bit to get going but he's very honest, probably a bit underrated," Williams said.

He said Shuka was unlikely to head to the Sydney carnival but a victory at Ellerslie would make him consider Brisbane, possibly for a race like the Doomben Cup.

Williams also starts Etoile Filante, who at her last start ran third to subsequent Auckland Cup winner Who Shot Thebarman in the Avondale Cup.

"She didn't get much of a run and should probably have run second that day," he said.

"Entering this race was a bit of an afterthought but she's well and next year she's going to have to race these sorts of horses."