Looks like Johns did something to his knee and had to undergo and MRI yesterday. Not sure what the severity is but Saban is supposed to address the press after practice today so when someone gets word we'll get it posted.
I know that Saban didn't address it in the pc but I wasn't sure if that was due to privacy issues or because it wasn't a huge deal. Looks like it was a mild injury if anything.
[[EDIT 2:50 pm]]
As far as their being no validity to it, I think that there is. For every person who has no idea about it and says it's a rumor there is another (on multiple sites) that are saying that it is in fact true that there was an MRI done. Some of the stuff I'm seeing now suggests that JJ had an MRI done but it was exploratory, and that it was not because of injury but because of lingering knee pain.
I'll just say this; I personally have not seen a statement yet from anyone including the writers for sites like BamaMag or Rivals (who have access to this info) that have said he didn't have an MRI or that he wasn't injured. The company line so far is simply that, "JJ was at practice and was not wearing a black jersey". That's it. That's a bit vague (maybe purposely so) and doesn't confirm anything other than JJ was at practice.
I'm not implying that there is a mass cover up or conspiracy here. It just means that we don't have all the info yet. Maybe it was bad info, maybe Saban didn't mention it because no injury occured at the time. I'm not sure.