He can't fight for long periods going backwards, Manny's legs aren't what they were a couple of years ago but Bradley's not elusive enough to avoid eating the straight left all night. He's got to mix it up on the inside and stop Pacquiao from getting effective punches off. Also the cuts could come into play, there's a real chance their heads will be clashing a lot and we saw in the first Morales fight how much the cut bothered him. I honestly feel Bradley is just the right fighter to give Pac all sorts of trouble right now and I'm picking him (tentatively) to win. I think he's slipped enough that a very good but possibly not great all-rounder like Bradley can beat him.
His adaptability could also be key, if things aren't working on the inside he could try and establish his jab or use a lot of movement and counters to frustrate him.