Mann-Rea is expected to be added to the Wallabies squad for the next two Tests against South Africa and Argentina following Tatafu Polota-Nau's worse than expected ankle injury.

But former Australian under-20s rake Siliva Siliva is refusing to contemplate the prospect of being called on by Australian coach Ewen McKenzie as he focuses on his comeback from ankle and knee surgery.

ACT Brumbies third-string hooker Mann-Rea spent two weeks in the Wallabies camp and sat on the bench for the clash against South Africa two weeks ago.

Mann-Rea is rated as the ninth-ranked hooker in Australian rugby, but an injury toll which has already claimed Stephen Moore, Nathan Charles and Polota-Nau, has catapulted him into Test contention.

Polota-Nau faces two months on the sideline, threatening to rule him out of the Wallabies' spring tour of Europe.

Siliva is set to make his comeback in three weeks which could put him in contention, while 33-year-old journeyman Mann-Rea, known as Bongo, looms as one of the oldest players to make their international debut.

"Bongo's got a really good engine on him, he's a really reliable footballer, low maintenance and he rips in," said Brumbies forwards coach Dan McKellar.

"He won't let the Wallabies down if he gets a chance. Josh took a punt to come to Canberra and backed his ability.

"He probably wasn't happy with how his career had gone ... Bongo is the first to admit he didn't take his opportunities, but he's certainly taken this one.

"It's a good story of persistence, he's battled away and he deserves all the accolades that come his way."

Mann-Rea played for the NSW Country Eagles against Brisbane City in Lismore on Sunday.

The Wallabies go into camp on Friday before flying to South Africa.

The two-game Rugby Championship trip to Cape Town and Argentina means it's unlikely Christian Lealiifano or Joseph Tomane will play for the Canberra Vikings against the Sydney Stars on Saturday.

Brumbies prop Ruan Smith has also been ruled out with an ankle injury while Henry Speight is six weeks away from making a comeback from a hamstring injury.

Siliva's three-year stint at the Brumbies has been plagued by injuries.

He had knee and ankle operations earlier this year, which prematurely ended his Super Rugby season and has put his Test ambitions on hold.

But the 23-year-old is rated as one the best young hooker talents in Australia and will make his comeback in the Canberra VIkings' line-up next month.

If he performs, it could put him in selection contention for a Wallabies berth.

"I kind of do want to rush but at the same time I don't," Siliva said.

"My body will tell me when I'm ready to go. I'll see what happens after that. I just want to play some football, it's been a long time.

"I just want to see if I can get back to where I left off. That's exciting and there are a lot of opportunities around as well.

"I'm not thinking about [Wallabies]. You never know what can happen, I would just rather concentrate on coming back a stronger player."

The Wallabies could be forced to head to Europe for their World Cup dry run without an experienced rake with Polota-Nau suffering an ankle syndesmosis injury.

Polota-Nau played just 40 minutes on his return from a knee injury.

He will certainly miss the Wallabies' next three Tests in Cape Town, Mendoza and the Bledisloe Cup Test in Brisbane on October 19.

"We don't think it's surgical at the moment but it's clashing with that [the spring tour] timetable so it's making it difficult," McKenzie said.

"The question is whether it goes to surgery or not, that's always going to be four weeks [recovery] just to look inside, but we're not at that point yet."

The Wallabies will name a 28-man touring squad this week for their two-week tour of South Africa and Argentina.