The midfielder is said to be in negotiations with the Glasgow club regarding an exit payoff following a training ground bust-up which led to a six-week suspension.
Barton, 34, was at the center of a fracas with teammates including Andy Halliday after the Ibrox side had fallen to a 5-1 defeat to Old Firm rival Celtic in September.
The one-time capped Englishman had been ordered to return to training with the development squad after his ban had been lifted, but the drama has taken a fresh twist.
With Barton now having handed a sick note to the club, negotiations over a severance package look likely to speed up, with some outlets suggesting the player could be released from his contract within 24 hours.
It has also been said that Barton, who makes 20,000 pounds ($24,790) per week, could leave Ibrox with as little as two months worth of wages.
