Led by a breakthrough performance from enigma Ryan Harris, South Australia wrapped up their maiden Pura Cup win of the season to thwart Western Australia's bid for a berth in the final on an enterprising last day at Adelaide Oval.

Set 292 for victory after Redbacks captain Darren Lehmann sportingly declared at 7-366 on Sunday morning, WA slid to 4-14 before lunch and were rounded up for 230 inside the last hour.

The result leaves Tasmania and NSW to contest the decider, while SA escaped the humiliation of a first winless season for 30 years by clinching their final first-class match for the third time in as many summers.

"It's bitterly disappointing, we knew we had our destiny in our hands, we knew if other results went our way and we won outright we'd be playing in the final, it's not to be, it's disappointing, and I'm sure we'll take a lot of lessons out of this season," WA skipper Justin Langer said.

"Everyone said the spinners would play a big role but I always felt we'd have to get through the new ball and to their credit they bowled superbly."

A bold and often brilliant unbeaten 103 by Adam Voges kept the Warriors in notional contention until late in the final session, when Redbacks spinners Cullen Bailey (2-69) and Daniel Cullen (2-56) finished off the match.

Chief wrecker for SA was 27-year-old quick Harris, wicketless in three games before this one, in which he nabbed 3-48 on Sunday for match figures of 8-140.

In 17 previous matches he had taken just 22 wickets at 56.09.

"He's been excellent for us in Twenty20 and one day cricket this year and today he showed that if he believes in himself then he's right at this level," Lehmann said.

"Previously he's been tinkering with performances and this game he was man of the match and fantastic for us.

"He'll have to get fit and strong over off-season and hit the ground running next year."

Jason Gillespie (3-16) was also influential.

Swinging the ball at pace, Harris had earlier chopped the top off the WA batting line-up, yorking Justin Langer with his first ball.

Gillespie chimed in with the pivotal wicket of Rogers caught behind, though the batsman appeared the victim of a poor decision.

David Bandy (58) and Voges then added 119 in 212 balls for the fifth wicket, including 30 in their final five overs together against some untidy spin bowling, to give the Warriors some chance of a dramatic turnaround.

However Gillespie (3-16) struck twice in two balls in the first over of his second spell, cramping Bandy for room as he tried to cut, then uprooting Luke Ronchi's off stump with a speedy delivery that kept fractionally low on the worn surface.

That appeared to end the match, but Voges, Aaron Heal and Steve Magoffin fought hard until well into the session.

Magoffin dabbed at a Bailey googly and was clasped by a juggling Daniel Harris at slip, Danny McLauchlan was deemed lbw on the front foot to Cullen, and last man Ben Edmondson squeezed off bat and pad to Jason Borgas at silly point.

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