Papalii picked up the injury during Sunday's clash against the Sydney Roosters to close out Round 17 in what was a narrow two-point win for the green machine.
Papalii left the field inside the opening ten minutes of the game and was unable to return, with the Raiders' forward pack standing up in his absence to record the crucial win over the tri-colours. It was a win which raised the Raiders to sixth on the NRL ladder with 9 wins from their 15 games.
While the club have not confirmed the exact parameters around the injury to the veteran prop, they have stated he is aiming for a Round 21 return.
With the Raiders having a bye in Round 20, it means Papalii is slated to only miss two likely winnable games against the Gold Coast Titans and St George Illawarra Dragons before returning in Round 21 when the Raiders travel to Auckland for a clash with the New Zealand Warriors.
Papalii has formed one of the game's most damaging middle third combinations alongside Joseph Tapine at the Raiders in recent times, with the now representative retired Queensland star averaging 129 metres pergame and tackling at 96 per cent this season to go with 22 tackle breaks, 8 offloads and a try in his 12 games.
His role for the Raiders is critical, with Round 17 being the first time he has played less than 40 minutes in a game since his first hitout of the season, which came in Round 4 from the bench after missing the opening three games of the campaign with injury.
Papalii will likely be replaced in the starting side by Emre Guler for this week's clash with the Titans.