Yeah, I don't know what's happening. Hard to get a feeling for where the responsibility lies too. On one hand you'd expect the players to pick up some extra injuries in the beginning when you change the way they train, but we're talking about small muscle and soft tissue injuries, not long-term ones like we have suffered all season. Gotta wonder what Forsythe has done since he arrived and what his long-term projection for the team was. Safe to say that he must be below the curve at the moment.
Then again, the world cup screws things up for everyone. United are even worse than us; they have suffered 44 injuries this season. There's just an insane amount of physical strain put on players in the modern game, and Premier League makes it worse by being such a backwards league. Two domestic cups, no winter break and one game every three days for extended periods of time... situation's just untenable.
I think our situation is a mix of being unfortunate and not having a good enough squad. Wenger couldn't afford to rest Kos at any point because he was what tied the defence together. In itself that fact tells you that we should have done whatever was in our power to sign another centreback of that calibre in the summer.