Papali'i has signed a mega deal to make the switch to Concord from the start of next year following his stint with the Eels, but has spoken openly about being unsure if he will be willing to honour the deal moving forward.
The second rower, rated as one of the best in the competition and set to play his first grand final with the blue and gold on Sunday, was speculating about his future as recently as this week, suggesting he would confirm his decision for next year following the decider against Penrith.
But Arthur's comments will allow Tigers fans to breathe easy, suggesting the forward will make the move to the joint venture, where he will be coached under Tim Sheens.
“Isaiah will be going to the Tigers,” Arthur said.
“He would have liked to have stayed but he has made his decision and he has too much integrity as a person to renege on his Tigers deal.
“He has made his commitment to them so that boat (Papali'i staying at Parramatta) has sailed.
“He is going and I wish him well.”
The Tigers have all but confirmed they will be unwilling to give Papali'i a release from his deal should he request one, with the gun forward effectively set to replace Luciano Leilua at the club next year after his move to the North Queensland Cowboys.
It's understood the Eels would have the cap space to keep Papali'i should he want to make the switch, although that would still need the blessing of the Tigers.