Another classy knock to Ed Cowan and career best figures for Pat Cummins have seen NSW in a commanding position at stumps on day two of their match against South Australia at the SCG.

The Blues lead South Australia by 104 in their must-win match at the Sydney Cricket ground after reaching 4-333 before rain halted play late on the second day.

Cowan (125no) hit his third century in 2017, and passed fifty for the sixth time this season as the Blues applied presser on the Redbacks who resumed day two at 5-169.

Cummins (4-54) spearheaded a dominant morning with the ball as the Blues ran through the Redbacks tail as the visitors lost 5-60 in the opening session.

Opening the batting for the Blues, Nic Maddinson was at his explosive best in his Sheffield Shield return blasting 70 from just 60 balls to get his team off to an ideal start.

Cowan continued the attacking after Maddinson’s dismissal, reaching 83no by tea.

His unbeaten 125 continues an impressive run of scores for Cowan, hitting 51no, 115, 0 and 212 in his previous four Shield innings.

Averaging 189 batting at three in 2017, Cowan continued at first drop for the Blues despite the return of Maddinson, and pondered whether he had been batting out of position as an opener for much of his career.

“I did think that,” Cowan joked after day two.

“I spent some time at three for Tasmania a few years ago and scored some runs there to, so maybe I have been a closet three my whole life pretending to be an opener.

“It’s just been nice to contribute again and nice not to waste good form.

“If I’ve learned one thing opening the batting it is that you don’t muck around with good form because often you’re facing the new ball and you can be sitting on your arse pretty quickly.

Cowan was happy with the overall performance from the team from the first ball to the last ball of day two.

“It was a bit of a perfect day for us, we’re 100 ahead and four down,” said Cowan.

“Early wickets were the key, if they had put on a partnership it could’ve been a very different day but our bowlers were excellent and hopefully we can pile on a few more.”

Despite believing national selectors may have put a line through his name, Cowan’s form is beginning to mount a stronger and stronger case.

“I’m the same age group as Shaun Marsh so if he’s not too old then maybe I’m not to old,” said Cowan.

“We’ll see, if I keep scoring hundreds… you never know.”