A four-game suspension means Nelson violated the policy multiple times. The first infraction puts a player into a confidential intervention program. A second violation brings a four-game suspension without pay.
Buffalo drafted Nelson in the fourth round last year. He started 12 games, catching 17 passes for 156 yards and a touchdown.
Nelson hasn't played in the preseason and had been overtaken by Jonathan Stupar for first-team reps on the practice field. Michael Matthews is Buffalo's other tight end after Derek Schouman suffered a knee injury in Thursday night's preseason game against the Indianapolis Colts.