WESTERN Australia has clinched a nailbiting one-point victory to kick-off the NAB AFL Under-18s Championships, with Matt Young booting a golden behind to down South Australia at Domain Stadium.

After leading by 31 points just before three-quarter time, the Sandgropers' advantage was whittled away as the visitors dominated the final term and leveled the scores thanks to two clutch Izak Rankine majors. 

But WA's defence stood tall late as SA desperately searched for the match-winning score, and surged the ball forward for Young to take a mark 40m out directly in front in extra time.

The 187cm forward took his time over the kick before pulling his set shot just wide, but it was enough to clinch a gripping 10.14 (74) to 10.13 (73) win.

U18: Fixtures, results and news

It was a heart-stopping finish to Peter Sumich's debut match as WA coach, and a high-quality contest throughout.

"Probably at the beginning you didn't know what to expect from this group – that was probably the hard part – but now what they dished-up you know what they can do," Sumich said.

"Hopefully they can continue that on. I thought they were very good with their pressure, tackling and chasing."

SA did all the attacking early (11-6 inside 50s) in the first quarter as potential No.1 draft pick Darcy Fogarty slotted both his side's goals to the first break. 

But WA bookends Oscar Allen (three goals) and Aaron Naughton took control as the hosts gained the ascendancy.

Allen banged through a superb set shot from the intersection of the 50m arc and boundary line before quarter-time, sparking a run of five unanswered goals for WA.

With rangy defender Naughton (15 disposals, four rebound 50s) and full-back Sam Taylor repelling SA's forward thrusts, the home team seemingly had the match under control.

"Oscar was really good early, probably faded a bit," Sumich said. "I thought Sammy Taylor and Naughton were outstanding down back.

"I liked (Taylor's) one-on-one contests. People probably underestimate Sam's body strength. He didn’t get beaten."

With rangy defender Naughton (15 disposals, four rebound 50s) repelling SA's forward thrusts, the home team seemingly had the match under control.

WA midfielders Brayden Ainsworth (26 disposals, eight clearances, one goal), Tom Joyce (21, four) and speedy wingman Jake Patmore (19) were on top and feeding a zippy forward line featuring dangerous Perth smalls Ian Hill and Sydney Stack (one goal apiece).

Such was Allen's influence that big-bodied Glenelg product Fogarty – who played mostly in attack – was shifted down back to start the last quarter.

Darcy Fogarty was one of SA's best. Picture: AFL Photos

But if the hosts thought they would romp to an easy victory, the Croweaters had other ideas.

From five goals down at the final change, SA surged with nine consecutive scoring shots – for 3.6 – and drew level when Rankine stepped up late.   

The visitors' engine room took complete control of the contest, led by Mitch Crowden (23 possessions), Jackson Edwards (23), Isaac Hewson (22), Charlie Ballard (20) and Rankine (20).

WA ruckman Jonathan Frampton (15 hit-outs, 15 disposals) and SA counterpart Callum Coleman-Jones (22 hit-outs, 17) were both highly-influential in an entertaining contest.  

WESTERN AUSTRALIA   2.4   6.7   10.12   10.14 (74)
SOUTH AUSTRALIA        2.2   5.3    6.6      10.13 (73)

GOALS
Western Australia: Allen 3, Stewart 2, Hill, Stack, Young, Ainsworth, Starcevich, 
South Australia: Fogarty 2, Houlahan 2, Rankine 2, Lukosius, Rozee, Rowe, Giro 

BEST
Western Australia: Ainsworth, Allen, Naughton, Taylor, Joyce, Frampton
South Australia: Edwards, Rakine, Crowden, Rozee, Giro, Ballard