Sam Konstas completed a terrific match with an unbeaten 151 on day three as New South Wales closed in on victory in the Sheffield Shield against a Western Australia side rocked by the withdrawal of injured skipper Aaron Hardie.

In a disastrous start chasing the 364-run target, WA lost openers Cameron Bancroft and Sam Whiteman along with nightwatcher Corey Rocchiccioli in the space of five deliveries just before stumps.

Seamers Ben Dwarshuis and Jack Edwards ran riot on a WACA surface that had appeared relatively docile.

NSW declared their second innings just over an hour before stumps after Konstas backed up his 71 in the first innings with a sublime 167-ball knock that included four sixes.

He played mostly orthodox but at good pace throughout, an innings keenly observed by national selector Tony Dodemaide in the terraces. Coincidentally, the finishing touches of his innings were taking place at the same time as Australia's familiar batting struggles during the second Test in South Africa.

"Feeling very good, feel like I've got a lot of clarity around batting and trying to put match-winning performances for the team," said Konstas with the declaration denying him a chance of overtaking his highest first-class score of 152.

"I feel I'm moving really nicely. Just to cash in with my start, I'm very happy."

WA's task has been made harder without Hardie, who was substituted out of the match due to a shoulder injury and replaced by uncapped batter Corey Wasley.

WA were dealt a major blow ahead of day three with news that Hardie, a seam bowling allrounder, would take no further part in the game having sustained the injury while batting on day two of the match. He clutched at his shoulder several times and looked increasingly bothered during his innings of 52.

The exact nature and severity of the injury will be determined as Hardie sweats on scan results. He will at the very least miss WA's upcoming One-Day Cup match against NSW and next week's Shield match against South Australia due to the mandatory stand-down period of 12 days after being medically substituted.

It is another setback for the luckless Hardie, plagued by injuries in a career that has yielded 15 ODIs and 18 T20Is for Australia. He had returned to bowling on day one having started the season as a specialist batter while he managed a knee issue, which ruled him out of Australia A's recent tour of India.

Relishing taking the leadership reins, Hardie had started the season in strong batting form at No.5 with an unbeaten 80 to lead WA to a thrilling two-wicket win over Queensland to open the Shield season.

Veteran Hilton Cartwright took the captaincy in Hardie's absence, but he spent a lot of time off the field during NSW's second innings after sustaining a finger injury while attempting a catch at first slip.

Cartwright will be available to bat on day four, but WA's mounting injury toll continued with Joel Paris - who led the side for most of NSW's second innings - looking uncomfortable with the home side facing a mountain of a task to avoid defeat.

After a composed half-century in NSW's first innings, Konstas' momentum continued as he took centre stage after being overshadowed on the first morning by Ollie Davies' 52 off 58 balls.

There was great anticipation over Davies, who smashed 253 off 225 balls in the previous Shield match against Tasmania. He did not waste time in the second innings after cracking Jhye Richardson's first ball through the covers for a boundary.

But for the second time in the match, Davies succumbed to a Richardson bumper after miscuing to square leg where Jayden Goodwin took a sensational diving catch.

Richardson did his best to haul WA back into the contest much like he did against Queensland when he took 5 for 19 in their second innings. But he could do little against Konstas, who swatted a short ball over the deep square leg boundary.

Fresh off his commanding 122 in the first innings, Kurtis Patterson unfurled several beautiful shots through the covers to combine in a half-century stand with Konstas.

Patterson couldn't go on it with after being trapped lbw by Rocchiccioli, who was soon on a roll after the wickets of Edwards and stand-in skipper Lachlan Shaw. Konstas was unruffled and brought up his half-century off 60 balls to ensure NSW's lead kept growing. He made 82 runs during the second session and reached his fifth first-class ton shortly after tea, waving his bat to his appreciative team-mates having registered the landmark off 136 balls.

He took the long handle to Rocchiccioli, with his best being a brilliant straight hit into the picket fences that left Dodemaide grinning from ear to ear.