The beloved prop forward was placed in a moon boot after rolling his ankle at training on Friday, with the club confirming the news on Monday.
Papalii will be monitored ahead of the minor premiers' first game of a fairytale finals campaign at GIO Stadium on Sunday.
He is expected to be named in the team on Tuesday but the Raiders will not take any risks with the 33-year-old given they have the double chance in finals and plenty of forward depth.
But it would be devastating for the Raiders to lose their spiritual leader from their push for a first premiership since 1994.
The veteran has become synonymous with the Raiders since his NRL debut in 2011 and is the most-capped player in club history.
Papalii's big-game experience shaped as crucial to a Raiders outfit that relies heavily on young stars Kaeo Weekes and Ethan Strange, who are both playing finals for the first time.
He highlighted his leadership qualities when coming out of State of Origin retirement to help Queensland win the decisive third match of this year's series.
Papalii is also one of only three players remaining from the Raiders' last grand final appearance in 2019 and was the star of the preliminary final win that confirmed their appearance in that decider.
His injury could pave the way for English recruit Matty Nicholson to retain his spot in the Raiders' 17 against the Broncos.
With most of the side's big-name players rested, highly-rated Nicholson faced the Dolphins on Sunday for his first game since May, when he was struck down by serious leg injuries.
Middle forward Trey Mooney, expected to depart the club at the season's end, is another option if Papalii needs time out.
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