Given the typical 12-month recovery time for this injury, that means Blair is likely headed for injured reserve and his 2019 season is over.
The injury also casts doubt on his availability for 2020.
Blair, 27, is a former fifth-round pick of the 49ers back in 2016. He’s currently in the final year of his four-year, $2.61 million contract and set to make a base salary of $630,000.
In 2019, Blair has appeared in nine games for the 49ers and recorded 21 tackles, three sacks and one fumble recovery.