This is the second such violation in as many years for Bryant, who was also suspended for the first four games of the 2015 season after failing multiple marijuana tests. During his suspension, he spent three weeks at a counseling facility in Houston.
Brian Fettner, another of Bryant's agents, confirmed he'll check into rehab Sunday to undergo further evaluation related to depression.
"We're all stunned, me included," Fettner told USA TODAY's Tom Pelissero. "We clearly miscalculated the issue. His isn't a party issue. It's a coping issue and a depression issue, and he's got to take care of it."
Fettner also revealed that Bryant is facing a suspension due to missing a drug test.
"He didn't fail a test," Fettner said to Jason Mackey of DKPittsburghSports.com. "He missed tests. But a miss is a failure to comply."
Steelers president Art Rooney II told reporters in January that he hoped Bryant was ready to put his troubles behind him.
"Martavis is a player who has tremendous ability and potential, and we just have to continue to work with him to make sure he takes care of his business off the field and puts himself in a position to be as great a player that he can be," Rooney said, according to the Pittsburgh Post Gazette. "We hope the experience he had earlier this season will have an impact on him."
If Bryant's suspension stands, Sammie Coates and Darrius Heyward-Bey figure to take on bigger roles behind Antonio Brown and Markus Wheaton. The Steelers also have tight end Ladarius Green, who signed with the team on Wednesday.
Bryant, a fourth-round pick in the 2014 draft, has caught 76 passes for 1,314 yards and 14 touchdowns in 21 career games.