WA crush SA to reclaim Shield top spot

South Australia coach Jason Gillespie was left searching for answers after his team became the latest victim of Western Australia's stunning start to the Sheffield Shield season.

The Warriors regained top spot on the ladder after crushing South Australia by an innings and 27 runs early on day four.

The defending champions have posted three wins and a draw from four games, while winless South Australia (two draws, two losses) are languishing in fifth and face a fight to avoid a third straight wooden spoon.

The Redbacks resumed on the final day in trouble at 6-66 in their second innings, still needing another 79 runs to make WA bat again.

Further hampering their cause, tail-ender Jordan Buckingham was ruled out of batting duties after injuring his right hand while sliding to save a boundary on Sunday.

There would be no final-day heroics from South Australia, with WA paceman Matt Kelly continuing his hot form as the visitors finished at 9-117.

Kelly, who snared 5-34 in the first innings, finished with 4-23 in the second to claim career-best match figures of 9-57.

Lance Morris followed up his 4-93 with 3-52.

But the real damage was done on day two.

After resuming on 5-267, South Australia were dismissed for 299, with WA finishing the day at 0-256 as Cameron Bancroft and Sam Whiteman scored centuries.

Whiteman (193) and Bancroft (135) went on to combine for a 308-run partnership - the fifth largest opening-wicket stand for WA in their first-class history.

"Disappointing is one word. Poor is another word we could use," Gillespie said after the loss.

"We're just not at the races. I feel like I'm a broken record.

"We show glimpses of good play, but we just don't string together hours or sessions to drive games forwards.

"We keep finding ourselves on the back foot, we keep getting it wrong, and we've got to be better.

"On the morning of day two, to lose 5-21 after doing all the hard work on day one, it's bitterly disappointing.

"It's something we've got to address quickly, because we can't keep doing the same things and expecting different results."

WA's results have been all the more impressive considering veteran opener Shaun Marsh is yet to play after injuring his calf while recovering from a knee injury.

Star paceman Jhye Richardson and Joel Paris missed the win over South Australia with minor niggles, with Kelly making the most of his call-up with a career-best display.

"I think everyone's clicking really nicely at the moment," Morris said.

"We had a few guys drop out - Joel Paris and Jhye Richardson, and we had Matt Kelly come in and a few other blokes who stepped up as well."

WA will be aiming to continue their hot form when they host South Australia in a top-of-the-table one-day clash at the WACA on Wednesday.