The competition leaders finished at 7-294 after winning an important toss and electing to bat on the Bankstown Oval pitch but late new ball wickets kept the visitors in touch.

Hughes put aside a modest BBL campaign to hit a polished ton, his first of the Shield season.

It was a much-needed boost for a side looking to bounce back from their first defeat and missing a host of starting regulars.

Hughes posted his century in the last over before tea only to be dismissed soon after the resumption for 103 in a 191-ball innings.

Gilkes belied his youth to offer more than able support after the Blues slipped to a precarious 3-133.

The 20-year-old looked accomplished in his just fourth first class outing and reached 83 off 132 balls, including three sixes, before he was caught brilliantly at gully by Jake Weatherald.

But his dismissal saw the tide turn as ever-reliable SA seamer Chadd Sayers (3-56) made the most of the new ball with the home side losing 3-21 during the final stages of the day.

Earlier, NSW-born Joe Mennie (4-82) shone for the Redbacks to claim the first four wickets, reaching 250 Shield wickets for SA in the process.

Mennie notably clean bowled Daniel Solway (22) with a superb delivery, before repeating the dose against Jason Sangha (5) minutes later.

Mennie was restored to the side in place of the rested Daniel Worrall despite the paceman's match-winning five-wicket haul last week against Western Australia.

The Blues are without experienced batsman Moises Henriques and Kurtis Patterson who are on Australia A duty, plus a host of internationals on Australia's tour of South Africa.

Australian Associated Press