SANTA CLARA -- Parys Haralson was expected to cede his starting linebacker spot to Aldon Smith this season. As it turns out, Haralson will vanish altogether after being placed Monday on the season-ending, injured-reserve list.
Although the 49ers didn't divulge Haralson's malady, it's believed he injured his left arm during the second quarter of an Aug. 26 exhibition at Denver.
Haralson has started 58 of the 49ers' past 59 games, including both of last season's playoff games. A seventh-year veteran, he has started 68 of the 86 games he's played as a 49er. But after a 14-sack rookie season, Smith was projected to replace Haralson in the starting lineup this year. Smith indeed started the exhibition opener but sustained a bruised hip and did not play in any other preseason games.
The 49ers announced that veteran Clark Haggans has been signed to a one-year deal and will fill Haralson's spot on the roster.
Sunday's starting outside linebackers for the 49ers' regular-season opener at Green Bay are expected to be Smith and Ahmad Brooks. Haggans, a 13th-year veteran released Friday by the Arizona Cardinals, is the only other outside linebacker on the roster.
Other pass-rushing options are to use Demarcus Dobbs in relief at right end or promote seventh-round pick Cam Johnson from the practice squad.
Coach Jim Harbaugh would only allow that Haralson is "working through something" when asked about his status after Thursday night's
Haggans, 35, will bring experience to the defending NFC West champions.
But first Haggans must deal with a potential three-game suspension from the league, stemming from a drunken-driving conviction in which he served two days in a Pennsylvania jail in June as part of his sentence.
Haggans is familiar with the 49ers and NFC West. A Torrance native, he spent the past four seasons with the Cardinals after an eight-year, Super Bowl-winning stint with the Pittsburgh Steelers.
Haggans has 46 career sacks, including three last season in 16 starts at left outside linebacker.
Haralson is the first 49ers player lost to injured reserve. Last season, the 49ers lost a league-low two players to injured reserve once the season began: wide receiver Joshua Morgan and defensive lineman Will Tukuafu.
Haralson hasn't been seen by the media since the Aug. 26 exhibition win at Denver, subsequently missing two practices and Thursday night's exhibition finale against the Chargers.
Haralson appeared to get hurt early in the second quarter in Denver. He lined up on the right edge and engaged in a block with tight end Joel Dressen. Knowson Moreno cut inside away from Haralson, who was standing toe-to-toe with Dreesen when Haralson suddenly looked at his left arm. Michael Wilhoite replaced Haralson on the next play; Wilhoite is now on the practice squad.