Ronald Blair, a valued member of the 49ers’ rotation on the defensive line, was declared out for the season Tuesday with a torn ACL in his right knee.
Coach Kyle Shanahan made the announcement that Blair will require season-ending surgery on a conference call with Bay Area reporters.
Blair sustained the injury while chasing down and throwing Seattle Seahawks quarterback Russell Wilson for a 1-yard loss in the fourth quarter of the 49ers’ 27-24 overtime loss on Monday night at Levi’s Stadium.
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Through nine games, Blair had 21 tackles and three sacks while serving as a backup edge rusher behind Nick Bosa and Dee Ford.
He was not credited with a sack on the play he was injured because it was determined to be a designed run play for Wilson.
Blair, 26, a four-year veteran, faces an uncertain future. He is scheduled to be an unrestricted free agent at the end of the season after finishing his original four-year, $2.5 million contract as a fifth-round pick in the 2016 NFL Draft from Appalachian State.
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The 49ers are expected to attempt to work out a contract extension or re-sign Blair in order to keep him around for the 2020 season. Defensive coordinator Robert Saleh repeatedly has expressed his admiration for Blair over the past three seasons.
Blair has 88 tackles and 13.5 sacks in 47 career games with the 49ers.