Rapoport also said there's a chance the Raiders will place Lynch on injured reserve:
The news was reported Friday after Lynch underwent an MRI earlier in the week.
The news follows head coach Jon Gruden's announcement that Lynch was dealing with a groin injury entering the team's Week 7 bye.
Before he hit the shelf, Lynch rushed for 376 yards and three touchdowns over Oakland's first six games. He also tacked on 15 receptions for 84 yards.
Doug Martin, who ranks second on the team with 27 carries, projects as Oakland's likely early-down replacement until Beast Mode is back healthy. The speedy Jalen Richard should also watch his role balloon considering he has posted a solid 8.2 yards per reception as a change-of-pace option out of the backfield.