Arlovski answered my question..

[jeht2000]

  He has NO chin!! Going into the fight with Fedor my question was not about how good Arlovski is on his feet or his boxing skills, but could his chin hold up. Well, I got my answer!!

[Rob The Long Island Cowboy]

http://www.mmapain.com/fedor-emelianenko-vs-andrei-arlovski-fight-video-affliction-day-of-reckoning/

In all defense here yes arlovski's chine has always been a question throughout his career.  he has all the tools.  just always seemed like he would benefit from a better team of trainers.  never quite reached his peak.  but if you watch he has the complete skill set.  just has trouble putting it all together.

secondly, fedor is no joke.  he has iron in those hands.  few guys could eat that right and still be standing.  knocked stupid?  debatable but certainly in a real real bad way. 

thirdly he was in a compromised position when he was struck.  the flying knee left him wide open.

To whit:

fedor is a dangerous striker.  a cold calculating fighter.  so precise in his technique that it looks like he's doing nothing.

andrei was always an enticing skill set just a c+ overall fighter.  moments of greatness but no where near fedor's league.