Per NFL Network's Ian Rapoport, Gathers has been suspended one game for violating the NFL's substance-abuse policy stemming from a September 2018 arrest for marijuana possession.
The police department of Frisco, Texas, said Gathers had less than two ounces of marijuana in his possession at the time of his arrest. He spent one night in jail before posting bond.
"Rico would like to express his gratitude and respect to the Frisco PD for their professionalism in this matter," the Cowboys said in a statement. "Rico sincerely apologizes to his teammates and the Cowboys organization for any distraction his arrest may cause as the team prepares to start the season."
A sixth-round pick by the Cowboys in 2016, Gathers spent his rookie year on the practice squad and the bulk of 2017 on injured reserve. The 25-year-old made his NFL debut last season, appearing in 15 games and recording 45 yards on three catches.
Jason Witten's return adds depth at tight end in Dallas. He will likely open the season as the primary tight end with Gathers and Blake Jarwin as the primary backups.
The Cowboys will open the season at home Sept. 8 against the New York Giants.