MRI tonight for Adrian Peterson

Typically it takes a day for teams to announce the full extent of a knee injury. So for the moment, at least, the Minnesota Vikings are calling Adrian Peterson's left knee injury a sprain.

Peterson appeared to suffer a more significant injury in the third quarter of Saturday's 33-26 victory over the Washington Redskins. An MRI will be conducted Saturday night in Minnesota to determine the full extent.

We'll keep you updated.