Ashton Agar and Shaun Marsh set up Western Australia to press for win

Ashton Agar and Shaun Marsh led a dominant display for Western Australia to give them a lead of 362 and set up a final day victory push against South Australia in the Sheffield Shield match at Karen Rolton Oval.

Having begun proceedings at 1 for 178, the Redbacks lost the centurion Jake Weatherald just the fourth ball of the morning as he hung his bat out to a Cameron Gannon delivery outside the off stump, and never again regained control of their destiny.

Agar followed up his century in the company of Josh Inglis by twirling his way to five wickets, starting with Travis Head when the South Australia captain top edged an attempt to clear the midwicket boundary. Gaining some appreciable turn out of the footmarks, Agar conjured a classic to bowl Harry Nielsen between bat and pad, and with a trio of tail-end wickets claimed his last four victims for seven runs in 53 balls - taking his figures from 1 for 96 in 22.4 overs to 5 for 103 in 33.

The displays of Agar, Lloyd Pope and Mitchell Swepson will all be sources of encouragement for the national selectors, as spin has played a far larger role in the first two Shield games than was the case for the vast majority of last summer on a succession of grassy surfaces.

The Redbacks had lost nine wickets for 134 on a friendly batting surface, giving the Warriors plenty of time to build their lead in the final session, and of the batsmen to appear on day three, only Brad Davis and the stranded Liam Scott could be even moderately happy with their efforts.

Sam Whiteman was an early casualty in Western Australia's second innings, touching a bouncer from Chadd Sayers through to Nielsen, but from there Marsh took complete control of the game with Cameron Bancroft working the ball around at the other end.

Marsh was able to take advantage of some loose stuff from Pope, who was far too variable in his length, while of the other bowlers only Scott's medium pacers were able to restrict the flow of runs in any meaningful way. This meant that the lead accrued quickly, even to the point that Marsh might have been able to consider a declaration late in the day.

Instead, he was content to bat through to stumps and in doing so reach a century scored with ease, with Bancroft falling to a terrific running catch by Tom Cooper from what became the final ball of the day. Agar's spin out of the footmarks will be critical to the tale of the fourth innings.