ST. LOUIS -- St. Louis Rams starting linebacker Jo-Lonn Dunbar was suspended Wednesday for four games for violating the NFL's policy on performance-enhancing drugs.
Dunbar, who was second on the team with a career-high 157 tackles last season, is able to participate in all team activities prior to the suspension, which begins with the season-opening game against Arizona. He will be able to practice and play in all exhibition contests prior to the opener.
Dunbar did not take questions from reporters Wednesday but issued a 41-second statement. He appeared emotional as he walked away following the comments.
"I just want to say that I did not take a performance enhancing drug," Dunbar said. "I mistakenly took something that prompted a failed drug test."
The 27-year-old Dunbar also will miss games against Atlanta, Dallas and San Francisco. He eligible to return on Sept. 27.
"I sincerely apologize to my teammates (and) the organization," he said. "I am deeply saddened by this. But I plan to serve my four-game suspension and get back to playing football as soon as possible."
The 6-foot, 235-pound Dunbar is the second St. Louis player suspended by the league this season. Running back Isaiah Pead will miss the opening game for a violation of the substance abuse policy.
Dunbar, who signed with the Rams on April 2, 2012, started all 16 games last season. He led the team in tackles for loss (23) and recorded 4.5 sacks.
Veteran linebacker Will Witherspoon is in line to replace Dunbar.
"You always feel bad any time a guy is going to miss a particular part of the season," Witherspoon said. "We're all going to support him."
Witherspoon, an 11-year veteran, is ready to pick up the slack left by Dunbar's suspension.
"If I'm asked to step in and start, then that's what I'll do," he said. "If not, I'll still be the veteran leader that I've always wanted to be."
St. Louis coach Jeff Fisher and general manager Les Snead were not available for comment. Most players were given Wednesday off. A one-hour special teams-only practice was held late in the afternoon.
The entire squad will participate in a full workout Thursday afternoon.