Ian Foster says the prospect of former All Black Tawera Kerr-Barlow playing for the Wallabies makes him feel a little uneasy.

Kerr-Barlow revealed his desire to play for the Wallabies thanks to World Rugby's new eligibility rules.

The 32-year-old halfback, who was born in Melbourne and moved to Hamilton when he was 13, is eligible to play for Australia under the new rules, where players are allowed to switch countries after 36 months of inactivity if they are either born in the country or have a parent or grandparent born there.

Asked about the potential switch after the All Blacks' team naming on Thursday, Foster admitted it made him feel uncomfortable and suggested he wasn't a fan of the new rules.

"It's just a consequence of World Rugby's eligibility laws isn't it. Kind of doesn't feel right to me but rules are rules and he's entitled," Foster said.

"All I know is the beauty of what he brought into the All Blacks camp. He's a quality person and quality rugby player. There's no judgement on that decision. What I remember from him is the influence he had in our environment, which was fantastic. So I guess to think of that going somewhere else feels a bit funny but like I said rules are rules and that's the way the game is going."

Kerr-Barlow rose to prominence with Waikato and the Chiefs, and went on to make 29 appearances for the All Blacks, including being a member of the 2015 World Cup winning squad.

The change in eligibility rules has seen the likes of Wallabies star Israel Folau, and former All Blacks Charles Piutau, Malakai Fekitoa and Augustine Pulu play for Tonga, but Kerr-Barlow could become the first to switch between two tier one nations.

His last match for New Zealand was against a France XV in November 2017.

Kerr-Barlow, who now plays for French side La Rochelle, said he would line up for Australia "without hesitation" if given the chance.

"Unlike New Zealand, Australia has a rule allowing players who are overseas to still be eligible for selection. I am available to play for the Wallabies," Kerr-Barlow told French publication Rugbyrama.

"I was born there. I have a lot of ties in this country and if the staff calls me I will go without hesitation. It would be a great opportunity but for the moment I am focused on La Rochelle."

His former teammate Sam Whitelock was less fazed when asked about the potential switch.

"I actually just found out before on the bus on the way back from the gym," Whitelock said.

"My initial thought was just let him play. It's just going to add motivation for us to play against him.

"He's a great player and he's done some amazing things for us but it's no different to any other player playing one or two games and then changing after a couple of years of not being available for that team."