Sam Konstas has continued to flag his strong potential as a superstar of the future, writing his name alongside Ricky Ponting in the history books with another Sheffield Shield century.

The teenaged opener put NSW in control of their clash with South Australia at Cricket Central, bludgeoning 105 from 225 balls after making 152 in a breakout first innings.

The hosts declared at 6-282 late on Thursday, with South Australia 1-7 chasing 389 runs for victory on day four after Nathan Lyon struck early to dismiss Connor McInerney without scoring.

Earlier, 19-year-old Konstas became the youngest player since Ponting to record two centuries in the same Shield game.

Australia's most successful Test captain achieved the feat as an 18-year-old playing for Tasmania against Western Australia in the summer of 1992-93.

"Obviously very special," Konstas said of matching Ponting.

"But hopefully we get the job done tomorrow and keep doing our basics well."

Konstas was given an extra life by Test wicketkeeper Alex Carey, who dropped a sitter before the teenager got off the mark on day three.

Having also missed a stumping in the first innings, Carey saved face with a diving catch that dismissed Nic Maddinson (eight) and continued the opener's meagre start to his second stint at NSW.

But Konstas nevertheless made the visitors pay.

He brought up his half-century off Lloyd Pope (2-84) in the 37th over with a four that rushed past extra cover so fast that Jordan Buckingham needed to jump to avoid the fence as he chased the ball past the boundary.

South Australia managed to slow Konstas down after tea as batting partners fell around him.

"They had different plans, they were bowling a wider line," Konstas said.

"I had to be a bit ruthless and cop my medicine a bit."

But the teenager finally brought his century up as the final hour of play approached, smacking a six over deep midwicket from Ben Manenti's bowling.

South Australia finally sent him packing just before 5pm, rival opener McInerney sprinting to long on to catch him off Pope.

Earlier, offspinner Nathan Lyon continued an impressive lead-in to the Test summer, finishing his first Shield innings of the summer with a five-for.

Lyon (5-47) ripped through the South Australian tail to ensure they were back in the sheds inside the first hour on day three, all out for 260.

Nathan McSweeney skied Lyon to deep square leg before Pope nicked off two balls later and set the stage for NSW to extend their lead, which was already 106 runs at the innings break.

Lyon expects to play two more matches for NSW ahead of the five-match series against India that begins in Perth late next month.