Cooper violated the NFL's steroids and related substance policy.
"I regret that I mistakenly took a stimulant that I did not realize at the time was banned by the NFL," Cooper, one of the club's more popular players, said through the team. "I support the NFL's anti-doping policies and understand that I must serve a suspension even though the stimulant that I took was not used before any game and was not used to enhance my performance.
"I apologize to the NFL, my team, my coaches, and to my fans, and I look forward to continuing to help the Chargers toward our goal of winning the Super Bowl in the upcoming season."
Cooper joins a list of current Chargers who have run afoul of the NFL's substance-abuse rules.
Linebacker Shawne Merriman has a four-game suspension on his resume for testing positive for steroids, as does fullback Andrew Pinnock. Plus defense end Luis Castillo tested positive before entering the league.
All of them have carried that stain on their reputation -- to some degree -- with them as they continued their careers. The same fate awaits Cooper, who is in line to lose more than $400,000 during the suspension.
"Coop has embarrassed himself, his family and the Chargers," general manager A. J. Smith said. "He made a mistake, and now he will move forward and get on with his life.
"Some people learn from their mistakes. Others do not. But I do believe Stephen Cooper will learn from his and move forward in a very positive way. Only time will tell."
This is the time of the year when Smith is at his best. Among the reasons the Chargers have risen from being an NFL dreg to being among the elite teams is Smith's handiwork.
And Cooper's suspension won't steer him long off his draft-day focus. Especially with an able backup like veteran Derek Smith already on the roster to cover for Cooper. Smith has said he Smith's acquisition was done separate of him knowing Cooper would be on the bench for the first four games. Cooper will be able to participate in the offseason workouts and the preseason games before his suspension begins.
Still, Smith doesn't like it when his team is bathed in bad light and he called Cooper's infraction "very disappointing."
Chargers coach Norv Turner also used that term.
"Obviously we're disappointed, just as I know Stephen is," Turner said. "Coop made a mistake and now must deal with the consequences. It's unfortunate, but we'll deal with it and move on."
Eric Weddle and Chris Chambers
Chargers general manager A. J. Smith goes into this draft with not much ammunition. But that doesn't mean that can't change, and quickly.
Smith has long proved he's not afraid to pull the trigger on big deals come draft day. He will always be remembered for drafting Eli Manning in 2004, then trading him to the Giants in a package which would eventually bring him Pro Bowlers in quarterback Philip Rivers, linebacker Shawne Merriman and kicker Nate Kaeding.
And even last year, he peddled lower picks to move up in the second round to snag safety Eric Weddle. With Marlon McCree allowed to leave during the offseason, Weddle is penciled in as a starter in 2008.
But while Smith's draft bounty includes one in the first round at No. 27, and not another one until the fifth round at No. 160, he could still make some moves. He has five total picks.
He figures to get two fourth-round compensatory picks next year after losing running back Michael Turner and Drayton Florence. So maybe he can trade the club's current picks in that round for the 2009 draft to move up in the 2008 draft.
Don't shed a tear, though, for Smith because of his lack of picks. The way he looks at, in lieu of a second-round selection, he has standout wide receiver Chris Chambers.
Minus his third-rounder, he has a potential starter in Weddle.
And devoid of a fourth-rounder, he has cornerback Paul Oliver, with that draft pick being burned last year in the supplemental draft. Oliver, who didn't see the field last year, could compete for a nickel or dime role in the secondary this year.
Whatever Smith decides to do he will dealing with the knowledge that the Chargers aren't in dire need of anything. That prevents him from having to overpay, with the bulk of his starting lineup which advanced to the AFC title game last season returning intact.
--The Chargers' schedule includes five games -- six if counting their night game in London which will air in San Diego in the morning -- in prime time.
"When I first saw the schedule, my first thought was, 'We should start practicing at night,"' coach Norv Turner said.
The Chargers have three Sunday night games, one on Monday and another on the NFL Network on a Thursday. Road-wise, the Chargers have five trips to or beyond the East Coast.
--Turner isn't overly concerned -- so he says -- about having so many players rehabbing this offseason. That includes QB Philip Rivers (knee), TE Antonio Gates (toe), DT Jamal Williams (knee), C Nick Hardwick (toe) and OLB Shawne Merriman (knee).
"The good thing is, if you are going to be in this situation, we have a number of veteran players who are at a point in their careers where they don't need quite as much time doing pure football," Turner said.
--Tomlinson said his knee has improved so much that he expects to take part in May minicamp workouts.
QUOTE TO NOTE: "There aren't many guys on the board in the second round that will be as good a player as Chris Chambers." -- Chargers coach Norv Turner, regarding the team's loss of a second-round pick this year, used last year in acquiring WR Chris Chambers from the Dolphins.
STRATEGY AND PERSONNEL
FRANCHISE PLAYER: None.
TRANSITION PLAYER: None.
UNRESTRICTED FREE AGENTS: None.
UNRESTRICTED FREE AGENTS (not tendered offers)
--RB Tyronne Gross (not tendered as ERFA).
RESTRICTED FREE AGENTS: None.
EXCLUSIVE RIGHTS FREE AGENTS: None.
--LB Derek Smith: FA 49ers; 2 yrs, terms unknown.
--OT Jeromey Clary: ERFA; terms unknown.
--WR Malcom Floyd: ERFA; terms unknown.
--CB Cletis Gordon: ERFA; terms unknown.
--CB Steve Gregory: ERFA; terms unknown.
--LB Marques Harris: RFA; tendered at $1.47M; terms unknown.
--DT Brandon McKinney: ERFA; terms unknown.
--G Scott Mruczkowski: Potential RFA; 3 yrs, terms unknown.
--QB Billy Volek: UFA; $9M/3 yrs, $3M SB.
--CB Drayton Florence: UFA Jaguars; $36M/6 yrs, $12M SB.
--S Marlon McCree (released).
--FB Lorenzo Neal (released).
--OT Shane Olivea (released).
--K Dave Rayner: Not tendered as RFA/Dolphins; terms unknown.
--RB Michael Turner: UFA Falcons; $34.5M/6 yrs, $15M guaranteed.