Collins' exact infraction is not clear, but sources said he did not fail any tests. Nowhere in the policy is five games listed as a potential penalty either.
Lawyers for Collins continue to appeal on his behalf, arguing that his violation of the policy allows for a fine but not a suspension, a source told ESPN's Ed Werder.
Collins will be eligible to return to the roster Oct. 18, the day after the Cowboys play the New England Patriots.
The Cowboys were not caught off guard by the NFL's decision, but coach Mike McCarthy said during his news conference Friday that "the timing of it is a bit awkward, but it's just something I can't speak of right now."
The suspension will cost Collins roughly $2 million and, per the collective bargaining agreement, 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. His appearance in Thursday's opener against the Tampa Bay Buccaneers was in question the week before kickoff because of a stinger issue that knocked him out of two practices.
Without Collins, the Cowboys could seek a replacement in a variety of ways.
Veteran Ty Nsekhe and Terence Steele, who started 14 games last year, served as the backup offensive tackles against the Buccaneers. If the Cowboys go for a tackle-for-tackle swap, then either could replace Collins.
"We've got a lot of experience last year of moving people around, but we'd like to keep moving forward with the guys who have been working at right tackle," McCarthy said. "Obviously [Collins], Ty and Terence have taken the reps there. ... We're eyes wide open. You have to be because things happen. We want to be able to have as many combinations as possible."
The Cowboys could also shift six-time Pro Bowl right guard Zack Martin to tackle and keep Connor McGovern at right guard. Martin started two games at right tackle last year before a calf injury ended his season. Martin remains on the reserve/COVID-19 list but is expected back in time for the Week 2 game against the Los Angeles Chargers.
Last week, McCarthy was asked about playing Martin at tackle this season.
"I would hope we don't have to go that way ever again," McCarthy said. "It speaks volumes about Zack Martin how he jumped out there and gave us the quality of play he was able to give us."
Collins' absence will not be the only one for the Cowboys' offense.
Wide receiver Michael Gallup left the 31-29 loss to the Buccaneers early with a calf strain that a source said could keep him out three to five weeks. He had four catches for 36 yards before getting injured in the second half.