Federer isn't exerting himself to win on opponents serves.He relies on one break because his service games are so good.His athleticism is very impressive for his age, though it is evident especially when pushed out wide he has lost a step.I've noticed thus far in this tournament he is not as lean as last year and is not moving as well. In terms of agility and speed, he looks very much like 2016 Roger which wasn't much different than 2015.Haven't seen he go into that gear with his backhand yet too, maybe it will come forth in QF or Semi
I would say at 36 he's managing matches better but not seeing him winning this overcoming the tough draw
However, with so many strong obstacles in his way, Nadal's probability of winning the title is most likely higher than Federer's
He is playing too solid and his defence is relentless hence seems to be the logical favourite