The Rams’ defense absorbed an early-season blow Wednesday with the NFL announcing that outside linebacker Jo-Lonn Dunbar will be suspended for the first four games of the 2013 season for violating league policy on performance-enhancing drugs.

Dunbar finished second on the team in tackles a year ago with 157 stops playing the weakside spot. An aggressive hard-hitting performer Dunbar was fourth on the team in sacks (4½) tied for third in interceptions (two) and forced two fumbles.

Dunbar will miss the Arizona Atlanta Dallas and San Francisco games to open the 2013 campaign. Until then he is eligible to participate in all team activities including practice and exhibition games. Once the suspension begins he will not be able to participate in any team activities until Sept. 27 the day after the Rams’ Thursday night home against the 49ers.

“First and foremost I just want to say that I did not take a performance-enhancing drug” Dunbar said following Wednesday’s Rams special teams practice. “I mistakenly took something that prompted a failed drug test. I want to say that I sincerely apologize to my teammates the organization Coach (Jeff) Fisher (general manager) Les Snead my family and friends.

“I’m deeply saddened by this but I plan to serve my four-game suspension and get back to playing football as soon as possible.”

So what was the banned substance?

“I just don’t want to get into that right now” Dunbar said. “That’s something we don’t want to talk about — we just want to move past.”

That was the only question the media was allowed to ask Dunbar who tearing up was then whisked away by the Rams media relations department.