It's simple, they are all just doing their jobs and playing on the same page and as a team. As talented as Collins is he's a liability when he's playing for stats instead of playing as part of the unit. I think Belichick was dealing with a defense where a number of key players were more focused upon their impending free agency than they were their opponent that week and playing as part of a unit, the Collins trade and the Sheard benching were his way of getting them focused on the job in front of them. However that only works if they succeed in the weeks after those moves, and that's exactly what happened, so now you have a defense that believes in their coaches and is focused upon doing their individual jobs as part of the unit.
