Western Australia 241 and 8 for 0 trail South Australia 264 (Manenti 86*, Paris 6-74) by 15 runs
Western Australia quick Joel Paris shredded South Australia's top-order to leave their Sheffield Shield game in the balance after day two.
After bowling WA out for 241, the Redbacks made 264 with Ben Manenti top-scoring with 86.
Paris, playing his first Sheffield Shield game of the season after recovering from a hamstring strain, took the initial five wickets and finished with 6 for 74, his sixth five-wicket haul in a first-class innings.
South Australia resumed on 27 without loss and soon were in Paris-inflicted strife. The left-armer began his wicket-taking spree in the first over of the day, removing Henry Hunt, who attempted an off-drive to a fullish delivery but edged to wicketkeeper Josh Philippe.
Paris next dismissed Daniel Drew lbw for a duck with a superb inswinger which beat the right-hander, also attempting a drive, and struck him on the pads.
SA opener Kelvin Smith was his next victim - the left-hander trying to cut a ball which dipped in and hit the top of middle stump. Three balls later, Redbacks captain Jake Lehmann was bowled for a duck when he missed another Paris delivery which nipped back off the seam.
SA had lost 4 for 21 1 in the first eight overs of the day but WA had to wait another 31 overs for another wicket - again claimed by Paris. His fifth breakthrough came when McSweeney, playing an expansive drive to a widish ball, feathered an edge to Philippe.
WA landed another blow in the next over with spinner Corey Rocchiccioli having Jake Carder caught behind when the left-hander tickled a leg-side ball to the keeper.
Carder's dismissal left the Redbacks reeling at 109 for 6 but Manenti and Harry Nielsen steadied the ship with an innings-high partnership of 83.
The stand ended when Nielsen, who struck two fours and a six, fell to Cameron Gannon, edging to first slip from round the wicket, before Manenti increased his scoring tempo - he was ninth man out after hitting nine fours and two sixes in his 107-ball knock.