Rapana and Melbourne forward Lagi Setu were partnered on their Mormon mission in 2011 and became such close friends they convinced each other to reunite at the Raiders next season.

While Setu won't join the Raiders until next year, Rapana, who converted to rugby union and hasn't played NRL in four years, is looming as an immediate candidate to ease the Raiders' injury crisis in their outside backs.

The Raiders were already missing Edrick Lee (broken arm) and Blake Ferguson (suspension) before losing Sandor Earl (dislocated elbow) and Jack Wighton (groin) to injury on Friday night.

Raiders coach David Furner watched Rapana's return to elite rugby league with Mounties in NSW Cup on Saturday.

''I'm pretty confident I can play NRL this year, that's my goal,'' Rapana said.

''There's a lot of games left in the season and the run the Raiders have had with injuries, I'm pretty confident … but I want to play well in NSW Cup so I have every right to get a game.''

Rapana and Setu didn't know each other before being posted to the other side of the world for their religious calling.

In Birmingham, they bonded while studying the Bible and - as Rapana puts it - went ''knocking on lots of doors''.

''We lived pretty much like brothers - we'd do everything together,'' Rapana said.

''It's like you're living with your best mate.''

Rapana, who began in the NRL with the Gold Coast, and Setu, who played with St George Illawarra and Brisbane, would occasionally talk football.

When they did, it was joking about returning to the field together in rugby union.

Rapana finished his mission earlier and joined Super Rugby with the Western Force before moving to Canberra and training with the ACT Brumbies.

Setu, a schoolboy rugby union player, instead returned to the NRL and signed a one-year deal for this year with the Storm.

The Raiders had unsuccessfully tried to sign Setu in the past but this time they had Rapana's help.

''When he found out he could be coming here, I was the first person he called,'' Rapana said.

''I kind of persuaded him. He was like 'I'm not sure if it's right'. I said 'just come … let's do this.'

''He'll kill it, he's like another [Josh] Papalii, he plays very similar. I think with the Raiders losing a few second-rowers like Joel Thompson, he'll be a strong replacement.''

Rapana describes his return to rugby league as ''natural'', given he struggled in the rival code.

''There were times when I got back into union and wasn't really cracking it,'' Rapana said. ''I went through some rough patches, I was a bit gutted.

''I thought 'was leaving rugby league the thing I should have done?' There were all sorts of thoughts in my head. I've been given an opportunity, a second chance … I did enjoy playing union but it felt like I was missing something.''

As he details the sacrifices made during his Mormon mission - no TV, radio, relationships or drinking - Rapana says he has no regrets.

''Two years out of the game is a long time but, while I was over there, I learnt a lot about myself, a lot about life and a lot about my beliefs,'' he said.

''By sacrificing that time I feel God is going to bless me for doing what I believe in.

''I felt like it was a big sacrifice at the time but, looking back on it now, I learnt so much from it and I don't see it as a loss at all.''