"Matt was just a situation where we just have to see how he is," Harbaugh said. "It takes a certain amount of time. First of all, we're going to have to see if the surgery actually worked, if there's going to be improvement. That's a question mark, so he may be battling this thing all year just like he did last year. And then just how well he can move the knee and then push it, and then the next day, how he comes back and recovers and then what he can do the next day. Obviously, we're shooting for the opener there, and anything we get before then would be a bonus."Birk has missed the Ravens' first three preseason games, giving way to Bryan Mattison to start at center over that span. Offensive line coach Andy Moeller sounded about as curious as everyone else to see how Birk fared.