It's a horrifying, horrible play that was 100% accidental and also 100% avoidable. I'm not going to go into this any further than NHL players should be mandated to wear visors, because the concern is on Staal and his health.
If you're in the mood to see it, watch the gifs below:
That's about as scary as it gets. I'm not a doctor, but I think Staal probably broke something on the play. Looking at the bottom gif, I don't think the puck hit him directly in the eye (thankfully) but I do think it hit his brow and then hit his cheek.
Best case scenario? Staal has some serious swelling in his face and is otherwise fine.
Worse case? I'm not going there. Let's just hope that he's alright and isn't seriously injured.