With Kotoni Staggs entrenched as right centre it means 21-year-old Mariner and Selwyn Cobbo will battle it out in future for the left centre gig.
Cobbo will return to the right wing against Parramatta on Friday night at Suncorp Stadium for his first game for the Broncos since the disappointing loss to Canterbury in round 21.
It is a position he has handled well in the past but he started the season at centre while Mariner was on the wing.
Selwyn Cobbo appears set to compete with Deine Mariner for a centre spot at the Broncos in future. (Jono Searle/AAP PHOTOS)
Mariner shifted to centre in round 18 and, despite struggling at times, was strong in the 42-18 win over North Queensland in round 23.
He's yet to have done enough to claim the spot as his own but it is where he said he wanted his future to be ahead of the Eels showdown.
"Obviously NRL's hard and it's hard to be consistent but that's something I'm working on," Mariner said.
"I'm always going to be confident to play centre because that's a preferred position for me.
"That's a position I love playing but at the end of the day wherever the coaches think I'm best for the team, that's where I'm going to play."
Brisbane's greatest centre Steve Renouf played wing in the initial stages of his career before playing for a decade in his favourite position and Mariner wants to do the same.
"I played centre through pretty much through my whole junior league, all the way to now," he said.
"Wing was just a position to get some reps. I kind of had to build into centre (in the NRL) because it is a more defensive position than wing. It has been a good transition and I'm still learning every week."
Mariner, who has scored 17 tries in 19 games this year, is signed until the end of 2027.
Cobbo is on the Broncos' books until the end of 2025 and will no doubt be in demand to play centre at another club if Mariner beats him to the role next season.
Before that happens the Broncos, in 10th position on 24 points, are aiming to finish their season with three consecutive wins and sneak into the top eight to play in the finals.
"Obviously that was our goal from the beginning of the year," Mariner said.
"It's been a up and down season, but we definitely still have got a chance."
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