Gregory last played in a game for the Cowboys in 2016.
Cowboys defensive end Randy Gregory suffered a "substance-related relapse" in August, according to ESPN's Adam Schefter, and may face discipline from the NFL.
Gregory will suit up for Dallas' Week 1 matchup with Carolina on Sunday but could be disciplined by the league as early as next week.
A second-round pick out of Nebraska in 2015, Gregory has missed 30 of the Cowboys' last 32 regular season games. He was suspended for the entire 2017 season in January 2017 after violating the NFL's substance abuse policy. Gregory was reinstated by commissioner Roger Goodell in July.
Gregory last played in 2016, registering one sack in two games. He played in 12 games for Dallas in his rookie season, adding seven tackles.