Papalii, 31, announced his shock retirement from the Origin arena on Thursday, less than two weeks before Game One at Adelaide Oval on May 31.

The Canberra veteran has been an automatic inclusion in the Maroons' set-up in recent seasons, having played every game for which he was available since the beginning of the 2017 series.

No active player has made more Origin appearances than Papalii, who secured the first of his 23 caps in 2013.

But the prop found his role scaled back significantly in Slater's first series in charge, averaging only 27 minutes of game time despite starting all three games.

Papalii had told reporters as recently as last week he was still keen on playing for Queensland, but he makes an abrupt exit to pave the way for the next generation of forwards and focus on his commitments with the Raiders.

He informed Slater of his decision earlier in the week and joins Raiders teammate and NSW utility Jack Wighton in withdrawing from Origin consideration since the beginning of the season.

"I've loved every minute of my time playing for Queensland and representing the state, and I have memories from my time in maroon I will never forget," Papalii said.

"I want to thank all of the coaches over the years that have given me the opportunity to play for Queensland and all of the players who I have taken the field with."

The selection call leaves Slater to ponder his wealth of middle-forward options.

Tino Fa'asuamaleaui, Lindsay Collins and Patrick Carrigan played all three games of last year's series, while Reuben Cotter, Tom Gilbert and Jai Arrow were also picked for at least one game each.

All six men are available for Game One and will be jostling for selection with Melbourne captain Christian Welch, who missed last year's series through injury but has been a stalwart of the Queensland set-up in previous seasons.

Also in the mix are uncapped Corey Horsburgh and J'maine Hopgood - two of the form middle-forwards - and Tom Flegler, Jarrod Wallace and Mo Fotuaika, three outsiders who have previously played Origin.

Former Queensland coach Mal Meninga, who gave Papalii his Origin debut, said the retirement call left the Maroons in a "fascinating" position.

"There's so much talent coming through, including his (Raiders) teammate Corey Horsburgh," Meninga told SEN.

"It will be interesting to see who Billy picks

"I believe that the whole 17 is really important.

"Sometimes you even have your better players coming on (off the bench).

"Josh was a great starter and he was uncompromising.

"Lindsay Collins is also a really good starter, so it's going to be fascinating."

Ahead of his second series in charge, Slater thanked Papalii for his commitment to the Maroon jersey.

"I was fortunate to feel both the presence 'Papa' gave as a teammate and the confidence he gave me as a coach," Slater said.

"Josh's commitment and performance in his last Origin game typified his career in Maroon - heart, selfless and committed to his team, warrior of the Origin arena."

Australian Associated Press