Cowan (r): Will take on Samoa

The Wallabies meet Samoa in Sydney as part of their build-up to the Tri Nations, which is followed by the World Cup in New Zealand.

Cowan was originally overlooked for Robbie Deans' 40-man Tri Nations squad but will earn his fifth Test cap from the bench this weekend after Benn Robinson suffered a season-ending knee injury in training.

The 25-year-old edged out veteran Waratahs prop Al Baxter for the vacant bench spot after Sekope Kepu was promoted to the starting side at loosehead prop.

Cowan still faces an uphill battle to force his way into the 30-man World Cup squad to be announced on August 18, however.

Injured Reds loosehead Ben Daley (shoulder) and Kepu are both ahead of him at present, while tightheads Ben Alexander and James Slipper could easily be used on either side of the scrum.

But Kiwi-born Cowan has every intention of returning to his homeland with the Wallabies in September-October.

"With the way that all the front-rowers are looking at the moment everyone's got an opportunity, especially myself, so I'm really looking forward to the next couple of weeks and then looking forward to the World Cup...fingers crossed," Cowan said.

"Unfortunately I hadn't made the 40-man squad initially so I was preparing to play for the Warringah Rats this week. Obviously circumstances have changed and here I am.

"The Western Force didn't perform that great this year and I think that kind of hindered opportunities for a lot of the guys to make this 40-man squad - but here I am and it's a rollercoaster ride and I'm riding it.

"Everyone strives to make that World Cup squad and that was always my intention."

Cowan, who made the last of his four Test appearances against Fiji 13 months ago, is on the comeback trail from a fractured cheekbone suffered late in the Super Rugby season.

He is confident his conditioning won't be a problem despite being limited to one club appearance in recent weeks.

"Thankfully I got a game last week for Warringah and that helped with my match fitness and it's got me back in the fray," he said.

Alexander says the Wallabies are expecting a torrid encounter against a near full-strength Samoa at ANZ Stadium.

"Obviously they're big blokes... they love the contact side of the game, they love belting people, they love running with the ball and they're very skilful," Alexander said.

"They've got some massive backs like (Alesana) Tuilagi on the wing and they've got some very skilful guys there too.

"They'll look to play an expansive game but also very physical so we need to be bang up for it otherwise we're going to be in trouble."