The former Wests Tigers star has asked Blues coach Sir John Kirwan for an immediate release after failing to make an impact with the Super Rugby outfit.
The New Zealand Rugby Union would need to ratify the release but that appears a fait accompli given Marshall's struggles in the 15-man game.
The 29-year-old has made spasmodic appearances off the bench over the opening 10 rounds but looks lost and down on confidence as he attempts to learn a new game on the run.
He is set to be dropped to Auckland club rugby after hitting rock bottom.
Marshall is likely to be welcomed back to the NRL, with a number of clubs sure to be interested in his services.
Struggling Cronulla head the list of suitors, with Melbourne, Parramatta and St George Illawarra among the other interested parties.
Marshall needs to find a club by the June 30 deadline for player registration.
The ex-Tigers playmaker left rugby league last year, saying he had achieved all he could in the game and was after a new challenge.
He talked of playing for the All Blacks but that dream now lies in ruin.
Wests Tigers have ruled out a play for their former star, who is likely to sign a modest contract on the back of a pay-out from the NZRU.
"We're as surprised as anyone that he's made a decision to leave," CEO Grant Mayer told Sportal.
"He said when he left us that he was looking forward to the challenge but obviously things have changed.
"There's always interest in good players but decisions were made last year and the salary cap is a different thing to manage.
"He made the call and we've invested in our young kids and that decision has been very good for us so far.
"He's a good quality players with talent so I'm sure there will be clubs looking for him.
"Whether it be in the NRL or Super League, I'm sure there will be a job for him."