Nelson is still eligible to participate in Buffalo's two remaining pre-season games. Once the regular season begins, he will not be eligible to return to the team until Monday, October 4, following Buffalo's Week 4 game against the New York Jets.
As ESPN's Tim Graham points out, the four-game suspension indicates that Nelson is a repeat offender of the policy, as all first-time offenders are placed into a confidential intervention program.
Currently second on Buffalo's depth chart at tight end behind Jonathan Stupar, Nelson has not yet recorded a reception in two pre-season games this year. With Derek Schouman suffering a knee injury in Thursday night's win over Indianapolis, the Bills could be in the market for a TE to start the season.