fedor lost to werdum purely because he made the mistake of staying in guard/range so that he could finish the fight. it is the fighter he is and once it has made him come unstuck. sure, he could be tentative in every fight and pull a gsp but he wouldn't be the fighter we know if that was the case. not only that but werdum has an incredible guard and has submiitted guys like fedor and werdum from that guard. his bjj background is no fluke.
If Fedor doesn't destroy Silva pretty quickly than I'll accept he has truly slipped. Until then he's just a human who made a mistake. If he's anything like the Fedor of old he should no worries finding Big Foots noggin :yep
Fedor will come out bombing and he won't have trouble in finding Big Foots head. Once he has him hurt then he'll go for the finish unless he has demons from the Werdum fight and wants to make his style a little more calculating rather than calculating while walking through fire.