Kevin Williams and Pat Williams both tested positive for performance enhancers. They're appealing, but if they're out for four games, the Vikings' season is over. They would be the second and third Vikings in the last two years to be suspended for performance enhancing drugs.
Specifically, they tested positive for "Water Pills", otherwise known as the diuretic Bumetanide. They can be used for weight loss, or, much more likely in this case, to mask steroid use.
So yeah. That's bad. And it means that this season has just been buzzkill after buzzkill.