NSW State of Origin star explains why his brother plays for Queensland - but will be supporting the Blues in the series decider

NSW Origin star Bradman Best has confirmed his brother plays for Queensland - but is adamant the in-demand teenager will be a proud Blues supporter in the series decider on July 17.

Baxter Best recently caught the eye while representing Queensland's under-15s schoolboys, and the Ipswich State High student is currently on the books of the Brisbane Broncos in a development deal.

On Sunday, older sibling Bradman Best was drafted in as a straight swap by coach Michael Maguire to replace the injured Latrell Mitchell ahead of game three, and the Knights fan favourite had no doubt Baxter will be cheering him on at Suncorp Stadium.

'My family moved to Queensland and he [Baxter] was playing [recently] in the under-15s Queensland schoolboys,' he said of the talented fullback.

'I'm sure he'll be going for me though, he'll be going for the Blues.

'He was born in NSW, it was just the family moved there ... so he's a Blue at heart.'

Best - who scored two tries on debut for the Blues in game three last year - is also poised to mark Knights teammate Dane Gagai in the Origin decider.

'It's going to be special. He's the old bull and I'm the young bull, it's going to be a good battle,' he told News Corp.

'He's one of the best centres. Obviously I train against him as well. It's going to be good, with KP [Newcastle fullback Kalyn Ponga] there as well.

'This is as big as it gets, it's exciting, and I can't wait for the challenge.'

Best will need to prove his fitness before lining up for the Blues, with the 22-year-old sent for precautionary tests on his hamstring following the Knights' win over the Raiders in Canberra.

Away from footy, the young gun is also dating Kayla Fenech, daughter of Australian former world boxing champion Jeff Fenech.

Elsewhere, Bulldogs match-winner Matt Burton has been called into NSW camp as the 18th man. 

The Blues last lifted the interstate shield in 2021, with Queensland coach Billy Slater chasing his third successive series triumph.