He may have seen him peripherally. I don't know. I was not in his helmet. However, I doubt he figured Sid would turn and look behind him and skate right into his line....like a mite hockey player may do. It was a dangerous move on Sid's part. Steckel (with no history of even being a physical player) played his line and an unfortunate event happened. The onous was on Sid for not remembering the most basic things they teach you though, not on Steckel for having the genetic code to make him 6'5".
Retribution (even from Tim Wallace) was absurd for this. And yes, I do want my #1 face off man on available to me the entire third period of a 2-0 game. I don't want him to have to sit for 5 minutes because the Pens were not ballsy enough to take action (which would have been uncalled for) at the time of the incident.
I am sure Pens fans are feeling great about not having the League leader in almost everything at the time of injury. I am not faulting Steckel entirely or Sid entirely. Both could have prevented this but you seem to only see one players action and not the others which is a total homer move.