I just saw this:

EDEN PRAIRIE, Minn. (AP) -Minnesota Vikings middle linebacker E.J. Henderson did not practice on Wednesday because of an unknown injury.

Henderson did some light jogging on the sideline but did not wear a helmet or shoulder pads during the portion of practice that was open to the media. He had eight tackles in the 27-13 win over Detroit on Sunday and is the Vikings leading tackler this season.

The Vikings certainly could use him this week against San Francisco and running back Frank Gore, who rushed for 207 yards last week.

This would really stink if he was out for the game Sunday.  I know it says unknown injury, but has anyone seen anything else indicating what the injury is?