NSW have enjoyed a return to form with the ball to have South Australia struggling at 5-169 after a rain-affected day one in the crucial penultimate-round Sheffield Shield match at the SCG.

Led by returning fast bowler Pat Cummins, the Blues found some form in a match they must win after two draws.

Former Test paceman Cummins, in his first Shield match for six years, bowled with good pace and bounce, taking a wicket in each of his two spells to end with 2-42 from 12 overs.

Cummins enjoyed strong support from fellow opening bowler Trent Copeland (2-61), who took two early wickets as SA slumped to 3-53 at lunch.

English leg-spinner Mason Crane collected his first Shield wicket on debut, having Tom Cooper (19) caught trying to loft over the infield.

Callum Ferguson remained defiant with the Redbacks No.3 ending the day unbeaten with a solid-looking 75.

Ferguson's unbroken sixth-wicket partnership of 48 with Alex Carey (23 not out) is the highest of the innings.

Rain forced players from the field on multiple occasions, with play ending for the final time just before 5pm AEDT with only 50.4 overs bowled.