Joey Barton is under investigation for allegedly breaking football betting rules, it is understood.
The controversial Rangers midfielder was banned from the club on Monday for three weeks after a training ground altercation following the 5-1 defeat to Celtic.
The Scottish Football Association and the Gambling Commission are looking into claims that the 34-year-old bet on Celtic to suffer a heavy defeat to Barcelona last Tuesday night. Brendan Rodgers' side lost 7-0 in their Champions League Group C opener in the Nou Camp.
The SFA has a strict no-betting policy on football games and if found guilty Barton could face a ban.
Barton is unlikely to face a major punishment if the alleged gambling was restricted to one incident.
Two former Rangers players are among those to have been punished for breaching the SFA's blanket ban on football betting.
Goalkeeper Steve Simonsen missed one game after betting on 55 matches and Ian Black earlier served a three-match suspension for gambling on 140 matches, including several he played in. The former Hearts midfielder scored in a 4-2 victory over East Stirlingshire after predicting his team would draw in an accumulator.
But a potential SFA charge will leave Barton even more vulnerable after his club suspension cast major doubt on whether he would play for Rangers again.
Barton was told to stay away for a further three weeks after talks with Mark Warburton and board members on Monday failed to resolve the situation which had seen the 34-year-old informally banished from the club for the previous five days following a training-ground row.
The former England cap has been told not to speak to the media after further angering Warburton by giving a radio interview last Friday when he claimed the manager's decision to send him home had been "strange".
But he has given further insight into his turbulent spell in Glasgow in newspaper interviews given last Wednesday - before news of the controversy broke - but published in this Tuesday's editions.
The former Manchester City and Newcastle midfielder admits feeling regret over his move to Scotland during a series of interviews with English-based journalists to promote his upcoming autobiography, No Nonsense, in which he claims he was approached by a third party to consider a move to Celtic just before he joined Rangers.
"I was never going to change my mind and let down Rangers," Barton told The Guardian.
However, on his general decision to move to Ibrox, Barton also said: "Reflecting on it, would I have made the same decision? Probably not.
"But I know that in time it will turn out to be the right decision. As tough as it is, adversity brings out the best in you."
The arguments with his team-mates - it is understood last Tuesday was not the first occasion - are put into context by Barton's comments on his approach to improving Rangers' indifferent start to the season.
"It's difficult when I'm playing at a level which, clearly, I've not played at before," the former QPR and Burnley player said.
"It's a much lower level and I'm trying to help people get to a higher level.
"They think me helping is me trying to say: 'You're not good enough.' It's difficult."
Celtic chief executive Peter Lawwell responded to Barton's claims that the Hoops were interested in him in a statement on Tuesday morning.
Lawwell said: "I think Joey's been had by a bit of a matchmaker here.
"I remember it well, we had just announced Brendan (Rodgers) as our new manager and I was with our company secretary in London at the time.
"An agent called me saying that Joey was going to sign for Rangers but he would really prefer to come to Celtic and were we interested in signing him, but it wasn't something we wanted to pursue.
"These things happen to players sometimes in football, but needless to say we wish Joey well at his new club."
An extract from Barton's autobiography published in the Daily Mail said that days before the player signed a two-year deal for the Light Blues he "took a call from an agent, who had been contacted by Peter Lawwell, Celtic's chief executive", adding: "The message he conveyed was straight and to the point. 'Is there anything we can do together? Can we have a conversation?'