The veteran midfielders had been in isolation from the rest of the squad since Monday morning for being "negative influences on the playing squad" though Fairfax Media understands that the coaching staff was also annoyed with alleged tactical dissent during Saturday night's 3-0 loss to Adelaide as Carle and Thompson were judged to have swapped roles.

Though, the PFA was informed by the club that Thompson and Carle were disciplined due to their negative attitude and influence within the squad.

"The only correspondence the players received as well was that they were negative influences on the playing squad," a PFA spokesman said.

Fairfax Media understands the club did not follow the procedures required to punish players for a breach of conduct under the A-League collective agreement, and did not submit a written explanation to Carle, Thompson or the Professional Footballers' Association for their actions.

The PFA threatened Sydney FC with legal action in response to the punishment, but reached an agreement on Wednesday afternoon that will allow Carle and Thompson to return.

"We are pleased the players are now able to rejoin the group in accordance with their rights under the collective bargaining agreement," PFA general manager Adam Vivian said. "It is our hope that there are no further instances of this practice of excluding and isolating players in the A-League as it has no place here."

Carle's representative, Tony Rallis, expressed his disappointment with how the situation was handled by Sydney FC, in particular the mixed messages surrounding the reason for his punishment. Media outlets reported that Carle was involved in a heated argument with Farina over tactics and had been a negative influence within the dressing room, but Rallis denied those accusations, which he suggested came from a club member.

"At no stage did Nick Carle refuse to play at number six; he's played there all year," Rallis said. "If people from Sydney FC's dressing room are saying these comments, I question their agenda. Certain other people at Sydney FC – and I'm not referring to [Scott] Barlow, [Tony] Pignata, Farina or Vidosic for that matter – have, in my opinion, been mischievous in leaking untruths."

Carle was not available for comment but his representative denied the former marquee player had a fallout with Farina and is eager to resume training.

"If his attitude was the problem, why did Frank Farina tell him two weeks ago that his professionalism and work ethic has been fantastic despite being dropped?" Rallis said. "Nick and Farina had a discussion that will remain private and he still regards Farina as a good man manager despite this situation."

It's not known if Farina will select Carle or Thompson for Saturday's match at home to Perth Glory despite being eligible.

Meanwhile, this Sunday's match between Brisbane Roar and Newcastle Jets will be overseen by the first foreign referee in the league's history.

Takuto Okabe, who has been the referee in 124 J-League matches, will take the whistle as part of a referee-exchange program between Football Federation Australia and the Japan Football Association. He will be assisted by Ashley Beecham and Brad Hobson and fourth official Alan Milliner – the trio set to run the lines of Japan's friendly with New Zealand later this year.

"We have a strategic plan and one of the important aspects of that plan is to offer our referees meaningful international experience, which will enable them to become better referees," said FFA referees director Ben Wilson. "Part of that strategy is the exchange program with the JFA and we are excited about having Takuto Okabe referee the A-League match on Sunday ahead of the round-24 match when an equally experienced Japanese referee will take control of the Heart versus Mariners game."

with Sebastian Hassett