Dallas Cowboys defensive end David Irving has been suspended for the first four games of the 2017 season for violating the NFL's policy against performance-enhancing drugs, the league announced Wednesday.

Irving, who started two of 16 games last season and finished with four sacks, will be eligible to return to the Cowboys' roster on Oct. 2. He is able to participate in all offseason and preseason practices ahead of the regular season.

Irving appealed the suspension in May, after a source told ESPN that the issue stemmed from an over-the-counter substance Irving used in an attempt to endorse the product.

He also had five tackles for loss, a team-high 26 quarterback pressures, five pass deflections and four forced fumbles last season.

Irving signed his exclusive free-agent tender earlier in the offseason and is set to become a restricted free agent after the 2017 season.

He is the Cowboys' second defensive lineman penalized by the league this year. Randy Gregory will miss the entire regular season for multiple violations of the NFL's substance abuse policy.

ESPN's Todd Archer contributed to this report.