Richburg missed all of last season after tearing a patellar tendon in December of 2019. He also had a shoulder injury and underwent hip surgery not long ago.
The 49ers signed former Falcons center Alex Mack in free agency.
“Yeah, Weston is going to retire,” Shanahan said. “I don’t know how that officially works, but that’s the word that I’ve been told.”
The 49ers restructured Richburg’s contract this offseason, clearing $6.875 million in salary cap space for 2021.