With Wes Welker in the slot it puts pressure on the strong safety to choose which receiver to cover.
If he chooses Welker, with Welker’s ability to adjust his route he often leaves that safety flatfooted and playing catchup. If he chooses a wide receiver, it forces a LB to try to cover him and leaves most of them in his dust. If it turns into a run in that 2nd scenario it takes that linebacker out of the play and If the runner can clear the line, it leaves open space to pick up a great run.
Anyway you cut it, without superb performance from opposing defenses, advantage Broncos!