McGahee injury

I am not much of a football fan and very rarely watch the sport on television and my football watching experience basically is attending 3 or 4 local college games a year with my oldest son who is quite a fan. Any football game that I watch in person is done with no interest in the outcome of the game as I really have no allegiance to any football team. This is kind of fun when a call may go against the home team and you can tell it was the correct call but at the same time you are sitting among thousands of people vociferously complaining and screaming about the call and also the "biased" officials who have some type of vendetta against the home team. It can be interesting to observe this though obviously I keep my mouth shut but may whisper into my son's ear that it was the correct call and he will usually knowingly nod.

Anyway, my son was watching the AFC Championship game on television between the Steelers and the Ravens. I was not watching though walked through the room just at the time of the McGahee/Clark incident so I saw it live and on the numerous replays. What bothers me about the play is that Clark made no (zero) attempt to tackle McGahee. He saw McGahee approaching and had a great angle and had him lined up and instead of trying to tackle him, he launched himself, with his hands at his sides, helmet first at McGahee and made contact, knocking him out.
Again, Clark made no attempt to tackle McGahee.

I am not "outraged" by it or anything as I know football is a brutal game but I am just struck by a safety who is usually the last line of defense making no attempt to tackle an opposing player on a big play in a big game and instead just looking to make a monster hit. In the end, from a football standpoint, it seems to be a low percentage play by Clark. Had he gone for a straight tackle, he probably has a 95% chance of bringing McGahee down. If he goes for the "human body missile launch", there probably is a pretty good chance that he either misses his target or that McGahee simply bounces off of him and stays on his feet and keeps going; maybe to the endzone.

There was no talk of this subject on the broadcast as the announcers were understandably focused on the apparent serious injury sustained by McGahee. I left the room just as McGahee was being carted off so if the announcers touched on this subject afterwards, I obviously missed it.

There is really no greater point and I am going to be terribly redundant here but I am struck by the fact that this was a big play in a big game and the defender made zero attempt to tackle the runner instead opting for a big hit.

If I happened to know a football coach, I guess I would ask him his opinion on the proper play for a defender in that situation though I think I know the answer.