Latrell Mitchell's arrival at South Sydney throws a much-wanted spanner into the works for Wayne Bennett heading into 2020.

Who misses out on a round one spot, and perhaps even before then, who is on the outer at Redfern?

In a backline filled with NRL experience, Mitchell's arrival casts doubt over the remaining outside backs' immediate future.

Mitchell, one of the most damaging centres in the game, has a desire to play fullback. That's a position he has not occupied since his debut season with the Roosters in 2016.

While not confirmed by Bennett or the Rabbitohs, the opportunity for Mitchell to play fullback appears to have been the big factor with further speculation at the club's press conference announcement on Monday.

How Latrell’s signing impacts Souths and other clubs

The Rabbitohs, who have struggled to find a mainstay No.1 since Greg Inglis's move to the centres post-ACL surgery in 2018, aren't short of options.

Alex Johnston has occupied the custodian role most with 54 appearances in the past five seasons but was moved to the wing by Bennett leading into the 2019 finals campaign.

He may be the odd-man out with his record on the wing at Redfern (61 tries in 68 games) far more impressive despite his own ambitions to remain at the back.

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Johnston has one year left on a three-year contract and is adamant he wants to see out that final season.

As he faced the media for the first time as a Rabbitoh on Monday, Mitchell said "the potential to play fullback is exciting".

"I've always come up as a fullback, I was never a centre," he said.

"I'm here to prove myself. Greg has left a great legacy. I'm not in a shadow of anyone. We're similar players and I get that. He's done well for himself and that's all I want to do.

"I look forward to the challenge."

Bennett's decision to sign former Broncos star James Roberts last May looked like a direct replacement after Inglis's retirement but only caused further selection headaches.

Braidon Burns, who impressed Bennett in the centres during a brief stint last year before succumbing to multiple hamstring injuries, is viewed as a long-term prospect at the club.

Campbell Graham, who represented Australia in the World Cup 9s and Prime Minister's XIII last year, is also a long-term option and is all but guaranteed a spot on the wing.

The predicament has left experienced campaigner Dane Gagai, who arrived at the Rabbitohs in 2018 on a lucrative four-year deal, as another player with question marks over their future at Redfern.

Latrell Mitchell joins South Sydney Rabbitohs

Gagai shifted to the wing when Burns and Roberts were fit. It appears that's where Bennett views the future of the Queensland State of Origin star.

"It's a hard decision and some of those longer term boys have played great footy for us but we couldn't go past the opportunity to get Latrell," Bennett said on Monday.

"I do [see Latrell as a long-term fullback]. I'm sure he won't struggle making that his own. He's got a lot of attributes I like."

Gagai and Johnston's immediate futures could be impacted by a decision surrounding Jai Arrow's arrival.

Arrow has agreed to join the Rabbitohs from 2021 but has been linked to a switch 12 months early.

The Titans would have to be compensated in some way, and it's a tough sell in January to move a player from a top-four status to a struggling club.

Suggestions of an early departure from Arrow were hosed down by Gold Coast Titans coach Justin Holbrook last week.

Rabbitohs General Manager Shane Richardson suggested Mitchell's immediate arrival would have little effect on the possibility of securing Arrow for 2020.

Adam Doueihi, who finished the 2019 season as the club's fullback, appears to be a logical choice offering a utility role from the bench, making way for Mitchell's positional switch.