Blackcaps v Australia: Gary Stead backs battling captain Kane Williamson

Kane Williamson's workload is up for discussion as the Blackcaps skipper navigates the most challenging period of his glittering career, says New Zealand's coach Gary Stead. 

One of the world's premier batsmen, Williamson leads the Kiwis in all three-formats of the game.

But New Zealand desperately need more from the 29-year-old in the third and final Test at the SCG, with Australia's plans to wear him down coming up trumps in Melbourne.

Blackcaps coach Gary Stead says Williamson is fine but he won't rule out alleviating some of the pressure around his leadership roles with the one-day and Twenty20 teams going forward.

"I think everything is up for discussion and it's healthy to have that debate around those things," Stead said.

"Like all players you go through ups and downs at times and some times are more challenging. This is obviously a challenging part of his career."

Williamson tallied just nine runs in two innings at the MCG, his fifth-worst return when batting twice in a nine-year Test career.

He is averaging 14.25 for the Trans-Tasman series, with MCG centurion Tom Blundell the Blackcaps' leading run-scorer despite not playing in Perth.

Williamson's captaincy has come under-fire, most notably from former skipper Brendon McCullum who has accused the Blackcaps of rolling over in the field.

Williamson won the toss in Melbourne but opted to send the Aussies in to bat only to see them pile on 467 runs.

But Stead said Williamson's Test could have been vastly different had a contentious umpiring decision gone his way on Sunday.

Williamson reviewed his second dig LBW dismissal but the umpire's call stood despite the ball looking to angle down the leg-side.

"You saw the dismissal yesterday; it was pretty unlucky I thought," Stead said.

"On another day it can been given not out and he goes on and makes a hundred and it changes that quickly."

Williamson, renowned for being one of world cricket's calmest characters, insists his mindset remains positive.

"It's one of those things where, cricket obviously, you do have to deal with failure a lot. It happens to everybody," he said.

"Wanting more is not an uncommon thing for anybody and certainly not for me. You're always wanting to improve.

"And in whatever role you have - whether its in the field as captain or with the bat."

Australian captain Tim Paine said Williamson's wicket remained their most prized but they had done well at wearing him down.

New Zealand have a multitude of issues heading to the SCG.

They must replace injured quick Trent Boult (broken hand), with Matt Henry most likely.

Spinner Mitchell Santner is desperately out of form, with the Blackcaps calling former NSW spinner Will Somerville into their extended squad.