Over at SBNation, our resident medical expert Ali Mohamadi took a look at Matt Schaub's lisfranc injury. Long story short: it's very bad. Not only will it cost him the rest of the season, it may also threaten his entire career:
Located in the middle of the foot, the Lisfranc ligaments connect the heel and the ankle to the toes. When they've been damaged, it becomes impossible to generate power or put any pressure on the foot, both fairly essential parts of the job description of an NFL QB.
As Mohamadi explains, it's a fairly rare injury in the NFL, with the most famous case being former Philadelphia Eagles RB Duce Staley. After surgery, Staley was never able to regain the mobility in his foot and was never the same player.
It doesn't necessarily mean that Schaub will suffer the same fate, but recovering from this injury will be a time-consuming, arduous and yet delicate process.