Ponga was overlooked for Game 1 of the series, with Reece Walsh selected in his absence before putting on a staring display for the Queenslanders in their series-opening win at the Adelaide Oval.
Ponga, who was believed to be in Slater's side until just hours before it was officially revealed despite moving to the halves at club level and battling with concussion during the first portion of the year, reportedly texted Slater before Game 1 to withdraw his availability for the remainder of the series.
The Daily Telegraph report that is born out of a desire to get the struggling Knights back on the right foot in a possible push to play finals football at the back end of the season.
Ponga promised he would fight to regain his position next year in Queensland's side.
“I reached out to him earlier in the week to let him know and wish him luck. I love Queensland and the Maroons jersey but I need to play more games and be on the field for Newcastle at the moment," Ponga told the publication.
“It was a really difficult decision to make but I will fight to win back my place in the Queensland side next year.”
The Knights sit outside the top eight, however, the incredibly close nature of the competition ladder means they are only a single point behind the eighth-placed Warriors, and five points behind the five leaders - the Penrith Panthers, Cronulla Sharks, Brisbane Broncos, Melbourne Storm and South Sydney Rabbitohs - as Round 14 prepares to kick-off.
Ponga's Knights have the bye this weekend, before taking the Brisbane Broncos away from home next weekend.