RENTON, Wash. -- Seattle Seahawks defensive end Bruce Irvin was suspended for the first four games of the 2013 season on Friday after the league announced he violated the NFL policy on performance-enhancing substances.

Irvin will be eligible to participate in all offseason activities and preseason practices and games, but will be suspended without pay for the opening four games at Carolina, home for San Francisco and Jacksonville and at Houston. Irvin will be eligible to return to Seattle's active roster on Sept. 30 following the Seahawks' Week 4 game against the Texans, but only after losing a quarter of his salary for the season.

Irvin, the Seahawks' first-round pick in the 2012 draft, was scheduled to make $814,645 in base salary for the 2013 season.

"I want to apologize to my teammates, coaches and Seahawks fans for making a mistake when I took a substance that is prohibited in the NFL without a medical exemption," Irvin said in a statement released by the team. "I am extremely disappointed in the poor judgment I showed and take full responsibility for my actions. I will not appeal the discipline and instead will focus my energy on preparing for the season so I can begin earning your trust and respect again. I look forward to contributing to the team the moment I return."

Irvin's loss could be a significant blow for a team that has become a popular pick to contend for a spot in the Super Bowl. Irvin was expected to start at defensive end with Chris Clemons likely to miss the start of the season while recovering from knee surgery after being injured in Seattle's playoff win at Washington last January.

Suddenly, Seattle's focus on addressing the depth on the defensive line in free agency won't be viewed as a luxury. Seattle signed Cliff Avril, Tony McDaniel and Michael Bennett in free agency to bolster a pass rush that was inconsistent for most of the 2012 season. Avril was the only true outside pass rusher the Seahawks signed, but all three, along with Irvin, were expected to upgrade one of the few weak spots on a rising young team.

Irvin finished his rookie season with eight sacks but had just one in the final six weeks of the regular season. With Clemons out, Irvin got the start against Atlanta in the NFC playoffs and appeared overwhelmed by the Falcons' offensive line while trying to be the main pass rusher on the Seahawks line. But his speed off the edge flashed at different points during his rookie season and was the big reason Seattle used the 15th overall pick on a rush end whom many pundits didn't expect to be drafted that high.

Later Friday, Irvin posted a lengthy message to his Twitter account, expressing remorse for his actions. Irvin, who had a troubled upbringing in Atlanta that included a brief jail stint as a teenager, noted his efforts to rebuild his image and said the suspension is another strike against him.

"I messed up and I feel so bad and have been depressed for weeks now," Irvin wrote. "I've had sleepless nights because I knew when this came out, I would let so many people down, including myself."

Irvin's suspension also continues a troubling trend of Seattle players running afoul of the league's policies on banned substances. Since 2011, five Seahawks players -- John Moffitt, Allen Barbre, Winston Guy, Brandon Browner and Irvin -- have received four-game suspensions. Barbre was later released by the team.

All-Pro cornerback Richard Sherman was also suspended last season for using a banned substance but won his much-publicized appeal last December. Sherman won by claiming there were errors in the chain of custody for his urine sample and that the tester made mistakes.