It seems receivers are scared to go over the middle. Having Landry back there, makes a HUGE difference. It will force quarterbacks to test the outside numbers, which will lead to more chances at picks for Revis, Cro, & etc. Not having to over worry about the middle of the field this year could be huge.
It's about rushing four and having more men in coverage. Also, Fitz expected man coverage when he got a hybrid man/zone. Expect fewer turnovers when there is film on this defense. It has nothing to do with players scared to come over the middle.