I agree with the first part. The defense could be better, but it's entirely unproven. For all the flack that the Ravens' defense catches, it is returning a DPOY winner and a strong DPOY candidate. They are also getting back a corner that didn't allow a touchdown in his last fully healthy season. They're replacing all their defensive departures with first- or second-round picks. Who on the Bronco's D should teams be scared of? Maybe Champ Bailey, but he's only getting older. Sure, the young guys could step up, but there's not way that the Bronco's defense should be considered very good until they prove it on the field.
Some players just fall off cliffs. It happened to Ray Lewis this past year. One season we're talking about how they keep beating Father Time, and the next, they look their age. Manning seemed like he could get it done, but how many hits is he going to be able to take? How is he going to play in cold weather after another year of wear on his body? He wasn't anywhere near good enough in the Divisional game to consider him an advantage the Broncos have over the other contenders.
He also had the critical lost fumble to let the Ravens tie in the third, not to mention that he didn't do anything after that fourth-quarter drive (which was apparently Fox's fault). That game-sealing interception was horrible, though. He looked like a rookie, except a rookie would have had the arm strength to make a better throw.