Half centuries to Cooper (87 not out), Alex Carey (66 not out), Jake Weatherald (59) and Jake Lehmann (57) have the Redbacks well placed at 5-315 at the SCG.

After debutant paceman Greg West had the visitors in trouble at 2-51 with two wickets in three balls in the opening session, the South Australians slowly worked their way back into the contest.

Cooper (87 not out) and Carey (66 not out) have put on a 130-run partnership and have a chance to press their advantage on Saturday.

"We've maybe just got our noses in front," Cooper said.

"It was a pretty even day. At stages we could have really got in front.

"It was a crucial last hour, we can edge in front if we capitalise tomorrow morning."

The Blues attack largely struggled on a lifeless SCG deck, Wests' opening spell aside.

At one point in his maiden first-class game he had figures of 2-0, having enticed Conor McInerney to edge through to Peter Nevill and then seen Kelvin Smith off, caught behind for a second-ball duck.

The 24-year-old was only called into the side after Cricket NSW allowed Trent Copeland to take mid-season leave.

Copeland has signed with the Seven Network to be part of the commentary team during the Australia-India Test series and was given permission to pursue his media career.

"The two wickets were pretty lucky but I'll take them on flat wickets," West said. "You've got to take them where you can at this level.

"It's a nice thing to get your first Shield wicket, let alone two in three balls. It's something I'll always remember and hopefully something I'll continue to do.

"Days three and four I'll continue to try and hit those stumps regardless of how many wickets I've taken."

Lehmann and Cooper put on 49 for the fifth wicket before the SA skipper was trapped lbw by part-timer Jason Sangha.

He came into the game with a chance to enhance his reputation as a Test-player-in-waiting having already brought up one century and two half centuries this season but failed to go on with it.

Australian Associated Press