A career-best innings from Jack Edwards elevated NSW to a promising position against South Australia as the Blues try to post their first win of the season in the final-round match.

NSW declared midway through the middle session at 9-447, with South Australia reaching 3-134 at the close on day two on Wednesday.

Daniel Drew (51no) and Jake Lehmann (13no) are at the crease for the Redbacks.

The other major contribution came from opener Kelvin Smith, who hit a confident 46 in his first Shield match for four years.

Allrounder Edwards led the way for the inexperienced Blues with an innings of 138 that included 20 boundaries and a six.

The 22-year-old's second Shield century eventually came to a close after 179 balls with a catch on the point boundary off the bowling of Nathan McAndrew.

Edwards and fast bowler Ben Dwarshuis were rarely troubled on the Karen Rolton Oval pitch in their 127-run stand for the eighth wicket.

Dwarshuis ended unbeaten on 60, having notched his first half century.

It was a day of career-highs with the NSW-born McAndrew returning 6-97, securing his maiden first-class six-wicket haul in the process.

South Australia's hopes of reaching the final ended in last week's penultimate round, while NSW are seeking to avoid a first-ever winless campaign in a 10-match season.