Shanahan added that Reed could end up miss around 6-8 weeks, per Eric Branch.
San Francisco has been without TE George Kittle the past few weeks and is managing several notable injuries on both sides of the ball.
Reed, 30, was taken in the third round of the 2013 NFL draft by the Redskins. He was in the final year of his rookie contract when he signed a six-year, $48 million deal that included $22 million guaranteed with Washington.
Reed was set to make base salaries of $8.25 million and $8.75 million over the next two years of the agreement when the Redskins released him earlier this offseason. He then signed a one-year deal with the 49ers prior to the start of the season.
In 2020, Reed has appeared in three games for the 49ers, recording 11 catches for 85 yards and two touchdowns.