The 19-year-old Papali'i limped off early in last week's 20-8 win over Gold Coast and has since been ruled out for up to six weeks with a medial knee ligament sprain.
He'll be replaced in the second row by ex-Titan Pulu, who has twice started on the bench this season and will line up alongside Tohu Harris and lock Ligi Sao.
As a result, fellow Warriors recruit Agnatius Paasi comes onto the bench, where he'll join another new face in Jazz Tevaga, who replaces Sam Cook.
Coach Stephen Kearney talked up Pulu's NRL pedigree.
"Leivaha did a wonderful job on the left edge (against Gold Coast), coming into the game so early after Isaiah was injured," Kearney said.
"It's tough for Isaiah being ruled out for a few weeks after the great start he had but fortunately we're able to call on Leivaha, as well as bring Agnatius onto the bench."
Elsewhere, the team retains a similar complexion to that which brushed aside South Sydney 32-20 and a blunt Gold Coast outfit in successive weeks.
The backline remains the same, with Roger Tuivasa-Sheck at fullback, Peta Hiku and Solomone Kata as centres and Blake Green and Shaun Johnson in the halves.
Up front, James Gavet and Adam Blair start at prop, with Issac Luke between them at hooker and Sam Lisone, Bunty Afoa and Paasi on the pine.
Simon Mannering and Gerard Beale remain injured.
While the Warriors have enjoyed a flawless start to 2018, the Raiders have not been so lucky, twice losing at the death to Gold Coast and then Newcastle.