Well, it's an international break, so I guess this was bound to happen. Idrissa Gana has injured his hamstring while playing for Senegal and is going for scans to find out how bad it is. At this point, we've got no idea what happened, and it might be simply a minor knock that'll keep him out for a few days or something like that.
But past history with Aston Villa players in the international break suggests that a "sky is falling" approach may be in order. Last season, for instance, saw Philippe Senderos injure himself in the October break. At that point he missed all of Aston Villa's matches before the November break, but he was almost back to health as we can tell by his inclusion on the bench in November. So, in November he rejoined Switzerland and... put himself out of contention for the rest of the 2014-15 season with another injury. All told? 29 matches from that.
There's no concrete sign that Gana will be out for ages, so panic shouldn't set in quite yet. But if you feel the first thoughts of panic settling in at the fringes of your brain, I won't blame you. Villa would be unquestionably worse off if they were to lose for any amount of time the man who has admirably replaced Fabian Delph.
I hate the international break.