Gagai, who was eligible for both teams, represented the Indigenous All Stars between 2015-17 but has chosen to represent another side of his family heritage in the revamped fixture.
Fan voting for the two sides that will take part in the Harvey Norman All Stars clash opened on Tuesday, with the NRL asking fans to have their say before coaches take that advice on board and select the two teams that will play for the Arthur Beetson Trophy.
Fans are allowed one submission for each team, voting for pre-selected players by their respective position.
Voting closes on January 30, with the fans' teams to be announced the following day. Official team announcements will be made on February 1.
NRL Senior Manager of Indigenous Strategy Mark Deweerd said voting is a great way for fans to be involved.
"The All Stars event is as much about the community as it is about the game itself," Deweerd said.
"The chance for fans to have an input into the selection of the teams is the only opportunity across the game that allows fans to vote for who they want to see play.
"As the teams will spend the week engaging with the local community, it would be great to see both the Victorian community and the broader population get behind the game, to not only celebrate a great game of football showcasing wonderful talent, but enjoy the cultural experience it has to offer as well."