The let-armer bowled with pace, swing and accuracy to collect figures of 4-57 and rip through the Western Australian top-order as NSW secured a 223-run victory on Thursday to strengthen their grip at the top of the Sheffield Shield standings.

A draw seemed likely after only nine wickets fell on the opening two days on a stodgy SCG pitch, but NSW's all-Test attack rose to the challenge dismissing WA for 191 and 128.

Josh Hazlewood picked up 3-7 on day four and Pat Cummins, who described the wicket as "like a tough Test wicket", collected four wickets in the match.

But it was Starc who looked the most dangerous in returning match figures of 6-102, getting plenty of movement with the new and old ball, and picking up four top-order wickets on day four.

After surprisingly playing just one Test in England, Starc opened the summer with just a single wicket in Shield match against Queensland at the Gabba.

But Starc says he has now found peak form, after an incredible 10-wicket haul against Tasmania in the ensuing Shield match and a strong showing in the recent Twenty20 internationals.

"The things I have worked on coming out of the Gabba game have worked really well, which is pretty pleasing for me," Starc said.

"Just to get a clearer mindset, and have that rhythm, which I have been pleased with."

Hazlewood was Starc's key partner in crime, narrowly missing a hat-trick after knocking over Ashton Turner and Cameron Green, before claiming the match-winning scalp.

Cummins, who described Starc as "bowling as quick as I have seen", bowled just one short spell on the final day for 1-16.

NSW's win, their fourth from as many Shield matches this season, finally arrived midway through the afternoon session just minutes before the Australian Test squad was announced.

Starc, Hazlewood and Cummins are favoured to start in next Thursday's First Test with James Pattinson and Michael Neser also named in the squad.

"It is (an) exciting (attack), and an exciting time to get back into Test conditions," Starc said.

"We have a really well-rounded attack, we can all take the new ball, we can all bowl with the old ball and reverse it as well. We have the No. 1 bowler (Cummins) in the world too."

Australian Associated Press