When the left knee of Vikings running back Adrian Peterson caved inward during a third-quarter tackle against the Redskins, it looked bad.
Based on the initial examination, a league source tells us it is bad.
The only question at this point is how bad the injury will be.
Per the source, it is strongly believed that Peterson tore the ACL. An MRI on Sunday is expected to confirm that specific injury.
The separate question is whether and to what extent other knee ligaments are damaged — the MCL, PCL, and LCL.
It could end up being the worst knee injury suffered by any Vikings player since Daunte Culpepper tore the ACL, MCL, and PCL in 2005. He never had the same mobility. Until Peterson plays again, Vikings fans will fear the same fate for their franchise tailback.