The 22-year-old lock is set to join Panasonic in Japan, despite being called into Dave Rennie's Wallabies squad during the Rugby Championship late last year.

Frost has been named in the Brumbies' starting side for a Super Rugby Pacific battle with the Fijian Drua at Canberra Stadium on Saturday.

But this season looms as his last in Canberra - for now - as Japanese clubs target overseas talent, with Wallabies back-rower Arnold shunning the chance to return home to sign a deal in Japan that will make him one of world rugby's top earners.

"It's a challenge. Really, it comes down to players and what motivates them, and what they want to do," Wallabies forwards coach and Brumbies mentor McKellar said.

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"If you want to earn very, very good money, then Japan is always going to be enticing, isn't it? If you want to stick around and still get paid well, and potentially still play Super Rugby and develop into an international player, then you understand that opportunity and money to go over to Japan or Europe is always going to be there. It's tough."

Frost's eventual departure will be offset by Darcy Swain's commitment to the Brumbies, with the 24-year-old closing in on a new deal to stay in Canberra beyond 2022.

The Brumbies are also on the verge of re-signing key trio Pete Samu, Ryan Lonergan and Lachlan Lonergan, which will keep them in the mix for the 2023 World Cup.

Rugby Australia is considering revising the Giteau Law by lowering the Test cap threshold and giving Rennie the opportunity to select a limited number of overseas-based players per series.

A change to eligibility laws will be crucial for the Wallabies, with Rugby Australia being priced out of the market for some top tier talent amid talk Taniela Tupou wants out at the end of the World Cup, while Reds and Wallabies second-rower Lukhan Salakaia-Loto could be bound for the UK on a deal worth more than $2 million.

McKellar has backed a change to eligibility rules but warned against a complete upheaval of the Giteau Law by Rugby Australia.

"It's never going to be a free for all. It's not like we'll be like the South Africans, who pick the majority of their squad from Europe," McKellar said.

"The Wallabies will always be selected primarily from Super Rugby franchises, knowing you've got to move with the times. Having the ability to pick three players, or however many it is from overseas, is important."

International raids on Australia's playing depth are not limited to Super Rugby sides, with club rugby stars in the sights of overseas teams.

The John I Dent Cup has become a hunting ground for Japanese clubs, with a handful of the competition's brightest talents jumping at the chance to join professional programs.

Queanbeyan trio Zeph Tuinona, Brendan Jimenez [Hino Red Dolphins], and Tony Alofipo [Suntory] have made their way to Japan, while Gungahlin pair Tom Haddad [Toyota Industries Shuttles Aichi] and Callum Macdonald [Shining Arcs] have also made the move.

"A lot of the Japanese sides are probably picking up those younger players and holding them for a couple of years, and then they qualify as locals," McKellar said.

"The players you're talking about, they want to take the opportunity when it presents. If you can't be in a full-time professional program here, then do you go to Japan and get paid to play and train professionally, and then potentially come back down the track?

"If you got a contract offer from a Japanese club, or you hang around here and work part-time, go to a public gym and train Tuesday and Thursday nights, it's a pretty easy decision, isn't it?"

SUPER RUGBY PACIFIC ROUND TWO

Saturday: ACT Brumbies v Fijian Drua at Canberra Stadium, 2.35pm. Tickets from Ticketek. Broadcast live on Stan.

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