The Jamaica international was sacked by the Latics after he was found guilty of sexual assault and actual bodily harm over an incident in a London nightclub, which occurred in December while he was on loan at Hull. Wigan chairman Dave Whelan confirmed King will never play for the club again following his conviction, but the player's agent, Tony Finnegan, said plans for appeals against both his sentence and his sacking are in place.
He told BBC Radio Five Live: "No one saw this coming in light of the evidence. He's very, very disappointed - because clearly, as he said in his evidence, it's mistaken identity. He didn't do that."
Finnegan added: "No one expected this. I asked Marlon and he said 'I'm not guilty, Tony - I didn't do it. I want the British justice system to find me not guilty'."
Finnegan expressed disappointment at Wigan's decision and the failure of the Professional Footballers' Association to support King, before questioning what might happen if the striker is released early.
"There was a union that didn't seem to back him in the shape of Bobby Barnes (PFA deputy chief executive) and the chairman of a professional football club that is going to say to everybody throughout Britain that this man will never play football again," Finnegan continued.
"The chairman's got a choice. If the chairman, which is his right, decides to sack Marlon King under gross misconduct, he would have to put that in writing, first and foremost. Then he has a right of appeal to the Premier League, in writing.
"If Wigan aren't successful in sacking this player and he comes out in three months' time and he wanted to be signed by another Premiership club, do Wigan allow him to go for nothing or do they seek a fee?"
Earlier on Thursday, PFA deputy chief executive Barnes admitted King had brought the situation on himself.
"I don't think anybody can deny that," he told Sky Sports News. "But I think it's important to bear in mind footballers are not divorced from society. They come from society, and people in society from all sorts of jobs will fall foul of the law."