The 49ers placed linebacker Malcolm Smith on injured reserve Monday, ending his season before it even began. Smith, who signed the most lucrative free-agent contract of any 49ers defender in the offseason — five years, $26.5 million — tore a pectoral muscle in Saturday’s practice. The recovery time for such an injury typically is five to six months.
Ray-Ray Armstrong, who tore a pectoral muscle last season, likely will step into Smith’s spot at weak-side linebacker but must hold off first-round draft pick Reuben Foster.
The two have different strengths. Armstrong, a former safety, is skilled in coverage while Foster, who played middle linebacker at Alabama, is excellent at attacking the line of scrimmage.
To help the depth in practices, the team signed linebacker Austin Calitro, who went undrafted out of Villanova.
At guard, the 49ers are hoping that medical exams this week explain the discomfort and swelling in Joshua Garnett’s knee. The former first-round pick had tried to gut it out through recent practices but is expected to have surgery to address the issue.
The 49ers are hoping he is not out long term. Zane Beadles will fill in at left guard during his absence.
The 49ers also suffered another injury at safety Saturday when seventh-round pick Adrian Colbert sprained his right ankle. Jimmie Ward and Jaquiski Tartt already have missed the bulk of the team’s training-camp practices with a hamstring strain and rib injury, respectively.
DeForest Buckner, George Kittle and Keith Reaser — who all have missed recent practices — appear poised to return in full today.