The Brumbies unveiled Slipper as a recruit on Friday after the 86-Test Wallaby was exiled by the Queensland Reds when he twice tested positive to cocaine this year.

He will be in a Rugby Australia targeted testing pool when he arrives in Canberra and the Brumbies are confident past indiscretions won't be recurring over the two-year deal.

Slipper's controversy aside, the Brumbies believe the quality he provides gives them the depth required to win Super Rugby titles even though they've already got the Wallabies' first-choice loosehead prop on their books.

McKellar, who is on a fact-finding mission in England and Ireland, spoke to Sio about Slipper's future before a deal was done and says the pair can work together to both become World Cup teammates.

"I've had plenty of conversations with James and we were comfortable with providing him with an opportunity to get his career back on track," McKellar said.

"He's going to add real quality to what is already a really strong front-row unit. You look at a team like the [Canterbury] Crusaders for example - Wyatt Crockett, Tim Perry and Joe Moody. All loosehead props.

"I think it can be really beneficial for James and for Scott Sio. We think we can manage it, especially in a World Cup year when players' workloads are going to be managed.

"James isn't coming to play five minutes off the bench here or there. You've got to manage the load of your front-rowers because it's so physically demanding.

"I had good discussions with Scotty and it was important everyone was across it. No one needs to feel threatened, it's about managing loads and using it to our benefit to ensure both players get the opportunity they need.

"Not just for us, but also for individual honours and to make sure come World Cup time, they're in a good place."

Sio will play his 50th Test for Australia when the Wallabies clash against South Africa in Port Elizabeth on Sunday morning.

He has been the mainstay in the Australian pack since the World Cup in 2015, while Slipper has struggled with injury and off-field battles for the past two years.

Slipper thanked the Brumbies for giving him an opportunity to resurrect his career. The 29-year-old has been working on his mental health since he was suspended for breaching the illicit drugs policy.

"The Brumbies have always had a long history of making players better through their program, so to get a chance to be a part of that is very exciting and something I am looking forward to," Slipper said.

"When I spoke with [Brumbies coach Dan McKellar] about 2019 and beyond I was very impressed and cannot thank both him and the Brumbies organisation enough for the opportunity to take my rugby career forward with them."

McKellar says the club will support Slipper to ensure his move from Brisbane to Canberra is smooth.

"You need to provide an environment where players feel supported and that's something we need to do for James and every other player who's involved at the Brumbies," McKellar said.

"One thing we've done at the Brumbies is provide people with opportunities. That's what I feel we're doing now after having long conversations with James and doing our research. James wants to play for a team that can have success and push for getting in the Wallabies again."

The Brumbies have one spot to fill on their roster for the 2019 season. That will be taken by an emerging prop in the coming weeks after the club casts its eye over young talent.

Brumbies forward coach Laurie Fisher said: "[Depth] is what wins Super Rugby championships.

"It gives us genuine quality and depth. It's a tremendous boost to the team and gives us that depth to compete at the highest level in Super Rugby.

"Props can't play for 80 minutes with the output you need. So to have two quality players, it's a seamless transition. There's just absolutely no downside to having two world-class players in the same position."