Novak has learned to play Federer to perfection. Aside from tactic of going to Roger's fh often, where Roger isn't that good defending, it's his mental approach.
Federer is the type of player that can go on a 4-5 game stretch where he makes an opponent feel inadequate. He will hit aces, come to net behind strong serves, fire bh/fh winners and even humiliate with a little dropper out of nowhere. The mistake some of Federer's past opponents have made is to panic and try to do too much. This results in gifting Federer points at precisely the wrong time, when already down 1-4 in a set. This exacerbates the problem. What Novak has learned to do is to accept these patches where Federer seems unbeatable and just stay calm... wait for a dip in level. The dip in level ALWAYS comes, here, Novak takes advantage. Over the course of a match, Novak banks on Roger not been able to be at top gear all the time and keeping it close. Eventually, something marvelous happens, Roger starts doubting himself and given he has the more risky game, makes more UFEs than Novak when it counts the most. Sometimes Novak gets into beast mode, like he did in AO last time they met but most of the time, Novak is just not panicking, forcing Roger to maintain his top gear all match, Roger can't.
Novak has also learned to play Nadal to perfection, that's another story.
