Western Australia 4 for 75 trail South Australia 155 (McInerney 43, Guthrie 4-53) by 80 runs
Western Australia youngster Liam Guthrie starred with four wickets against South Australia on a day where the bowlers dominated at the WACA.
Guthrie, a 21-year-old left-arm quick, claimed his career-best figures of 4 for 53 as the Redbacks were rolled for 159 after being sent in to bat.
But the visitors fought back late in the day to have WA 4 for 75 at stumps and leave the game evenly poised.
The WACA pitch was covered in live green grass and Mitch Marsh had no hesitation in bowling first in after winning the toss. But the visitors started very well reaching 60 without loss before Hilton Cartwright made the unlikely breakthrough.
Having not taken a wicket in his previous 15 Sheffield Shield matches he took two in his one and only over for the day. Jake Weatherald holed out to point for 25 before Jake Lehmann was caught behind.
Guthrie then ripped through the middle order. He bowled Test vice-captain Travis Head and Conor McInerney in the same spell. McInerney fell for a patient 43 from 144 balls.
Guthrie also took a catch and produced a run out before pinning Callum Ferguson lbw. David Moody also picked up 2 for 15 from 14.3 overs as South Australia were all out for 159 with only five players reaching double figures.
The Redbacks answered back in the afternoon claiming four wickets in 24 overs. Sam Whiteman was caught behind off Nick Winter before Cameron Bancroft was run out by Joe Mennie for 11. Josh Inglis and Marsh steadied with a 43-run stand but both fell in sight of stumps to Mennie and debutant Luke Robins respectively.