Currently based in France, the 32-year-old halfback stated overnight he wanted to play for his birth country.
Kerr-Barlow was born in Melbourne and grew up in Darwin with his mother Gail a halfback for the Wallaroos in the mid 90s.
He moved to Hamilton in New Zealand when he was 13 and after resisting overtures from Australian rugby he went on to play 29 Tests for the All Blacks, helping them to lift the 2015 Rugby World Cup.
His former Chiefs coach Rennie said on Thursday that Kerr-Barlow had recently reached out about playing for the Wallabies.
World Rugby's eligibility laws have been eased to allow players to make an international switch after 36 months of inactivity although they must have been born in or have ancestry in the transfer country.
"I had a conversation with him when he rang up just to say that if we got under any pressure, if there are injuries ... he's born in Australia, a former All Black, but the change of rules makes him eligible," Rennie said on Thursday.
Under national selection requirements Kerr-Barlow would need to commit to an Australian Super Rugby side to be available but Rennie said it was a positive he wanted to don the gold jersey.
"He's a great man, a hell of a player and you've got a guy who's a former All Black putting his hand up to play for Wallabies, that's a good sign," Rennie said.
While the move is flattering, Rennie felt the Wallabies were well-covered at nine with Nic White, Tate McDermott, Jake Gordon part of the current squad.
"We'll be loyal to the guys we've got, it's probably our strongest position.
"We got three excellent nines here and Ryan Lonergan behind that, but as we've seen this year things can change quickly so I will certainly keep in contact with Tawera.
"It's a hell of a resource in behind what we've already got."
Rennie was asked about whether there would be any resistance from World Rugby, with the rule change intended for emerging nations.
Ex-Wallabies star Israel Folau has already taken advantage, now playing for Tonga.
"That's open to debate but once you open the floodgates it's available for everyone I'd say," Rennie said.
All Blacks coach Ian Foster wasn't comfortable with the ground-breaking move with Kerr- Barlow becoming the first player to switch between two tier-one nations.
"It's just a consequence of World Rugby's eligibility laws.
"It kind of doesn't feel right to me, but rules are rules and he's entitled," Foster said.
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