Players cannot be suspended for positive marijuana tests under the NFL's collective bargaining agreement, but Collins' issue was multiple missed tests and trying to bribe the test collector, sources said.
The NFL initially was preparing to suspend Collins five games for his actions, but the NFL Players Association -- aware of the intended five-game suspension -- helped negotiate a reduction to what would have been a two-game ban.
Collins, however, appealed the suspension, and the appeal was heard by an arbitrator appointed jointly by the league and the NFLPA. The arbitrator not only rejected Collins' appeal but also ruled that, based on the evidence, the suspension should be increased back to the original five games.
Collins' lawyer is attempting an appeal of the arbitrator's decision, but league sources believe the suspension, which was announced Sept. 10, will not be reduced.
Both the NFL and NFLPA declined comment this weekend when contacted by ESPN.
He believed he had legitimate reasons for missing seven drug tests, one of which was scheduled for the day that Cowboys strength and conditioning coach Markus Paul died in November. Collins missed another drug test the day of his uncle's funeral.
Collins is not the first NFL player to attempt to circumvent the league's drug-test policy. In 2013, the NFL suspended Denver Broncos star Von Miller six games after he was caught attempting to corrupt the drug-test program with the help of a urine collector.
If his suspension is not reduced or overturned, Collins will be eligible to return to the roster Oct. 18, the day after the Cowboys play the New England Patriots.
The suspension will cost Collins roughly $2 million and, per the CBA, voids the injury guarantee worth $6.48 million in his 2022 salary.
Collins has started 62 of the 63 games he has played for the Cowboys since 2015 at left guard or right tackle. He missed 13 games in 2016 because of a toe injury and all of last season because of hip surgery.