On Monday, the MLB Players Association, on Sanchez's behalf, filed a grievance against the club seeking lost wages and service time.
At issue are the circumstances that led to Sanchez being optioned to Triple-A Albuquerque on May 4.
On May 2, Sanchez pitched in what turned out to be his final game of the season, giving up three runs on seven hits in 3 1/3 innings against the Mets at Shea Stadium. Two days later, he was optioned to the Minor Leagues.
The Marlins claimed at the time that Sanchez informed them of a sore shoulder after he was demoted. The union's stance in the grievance is the team knew beforehand that the 23-year-old was hurt.
Sanchez currently is on the Minor League disabled list. According to the South Florida Sun-Sentinel, Sanchez's split contract is costing him $214,000.
Entering the season, Sanchez was signed for $381,000, but he is now being paid as a Minor Leaguer, not what he would have made had he remained on the big league club.
Players on the MLB disabled list get paid their Major League salaries, plus they receive big league service days, which counts toward reaching arbitration and free agency.
The grievance process states that both sides must meet within 35 days in hopes of reaching a settlement. If that doesn't happen, then the matter ultimately could be decided by an arbitrator.
In late June, Sanchez had his shoulder examined in Birmingham, Ala., by orthopedic surgeon Dr. James Andrews. The righty underwent surgery to repair a torn labrum.
Sanchez is currently doing conditioning, but he hasn't started throwing yet. It is questionable whether he will be ready by Spring Training next season.
Sanchez was 2-1 with a 4.80 ERA in six starts this season.
As a rookie in 2006, he was 10-3 with a 2.83 ERA, and he threw a no-hitter against the Diamondbacks on Sept. 6.
Joe Frisaro is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.