The 25-year-old has engaged the services of Professional Footballers Australia chief executive Brendan Schwab to challenge United's decision to release him following his refusal to play for the club's National Youth League team against Melbourne Heart just over a week ago.

The former Brazil under-20 international, who is contracted until the end of next season, has been told not to come to training.

Coach Miron Bleiberg, who has been one of Robson's biggest supporters since bringing him to the Gold Coast as part of their foundation squad, was hesitant to go into detail when quizzed about the situation on Monday.

"I have a lot of respect for Robson as a player and I have a good relationship with him," Bleiberg said.

"But he did the wrong thing. Now it's being handled between employer and employee."

But Schwab said the PFA is adamant that Gold Coast United do not have the authority to end Robson's contract, which would also revoke his immigration status.

"As a consequence, Robson remains a contracted player and he is protected by our collective bargaining agreement," he said.

"If they are prepared to stand by the contract then this situation will be resolved immediately. If not, the legal process will continue.

"We are very strongly of the view that there's no basis upon which they can terminate his contract on the information we have so far - particularly given our concerns surrounding the reasons which he was told to play with the youth team.

"They basically go to the club's desire to sever this contract. There are no previous questions about his performance or conduct since he has been at Gold Coast United."

It is another disappointing development in the career of the enigmatic South American, whose first two years with United were blighted with injury and inconsistency.

During the most recent off-season, Robson was in career-best shape and was set for a major role in Bleiberg's preferred starting XI.

But after a less than impressive start to the new campaign, he was dropped to the bench for United's round three match with Brisbane - and when he came on, made a costly error that led to Roar's third goal.

"He was a big part of our plans, but we have big plans for a lot of players and see where we are," Bleiberg said.

"He had one or two off games, and that's why I asked him to play in the youth team - just to prove he can play a main role at that level.

"But he did the wrong thing, and that eventuated from the fact that he also wasn't that good (early in the season), or else he wouldn't have been asked to play in the youth team."

It is understood that Schwab is not pleased with the contractual environment for players on the Gold Coast.

The PFA chief said there is a decision pending on a 'very significant case' involving German midfielder Peter Perchtold, who was released by United at the end of last season.

"We are concerned their conduct is not helping the international reputation of the A-League," Schwab said.

"We've worked very hard to make sure our competition is attractive to an outstanding calibre of foreign players, who have made a hugely positive impact this year on the competition."