A corner of Peterson’s caliber allows them to slide McCourty or Harmon into the box on a full time basis in obvious passing situations. The play at both the CB2 and LB positions have been questionable and inconsistent against the pass.
Pats LBs actually haven't been targeted very much, perhaps because they've been "schemed out" of coverage responsibilities as much as possible. When they have been targeted (only 3.5% of their combined snaps), Roberts, HT and KVN have collectively allowed about a 60% completion rate for a 6.5 YPC (not allowing much YAC) and 1 TD. They also have 5 PDs/INTs as a unit.
As for CB:
Gilmore = 37 tgts (7.8% of snaps), 35% comp, 9.5 YPC, 5.4% TD/tgt, 24% PD/INT per tgt
J.Jones = 32 tgts (9.6% of snaps), 50% comp, 13.4 YPC, 6.3% TD/tgt, 22% PD/INT per tgt
JMac = 32 tgts (8.9% of snaps), 53% comp, 15.9 YPC, 3.1% TD/tgt, 16% PD/INT per tgt
... JJ and JMac have each gotten burned for a long TD. JJ gave up a 67-yarder to Westbrook (JAX) on a pick-play. JMac gave up the 67-yarder to Hunt (KCY). Those two plays blow up their respective YPC numbers.
Rowe = 11 tgts (8.1% of snaps), 64% comp, 15.1 YPC, 18% TD/tgt, 9% PD/INT per tgt
... Rowe's 2018 numbers are very similar to his 2017 numbers.
As a group, the Safeties have been the worst, mostly due to DMac's numbers from the Indy and KCY games:
Chung = 22 tgts (6.0% of snaps), 59% comp, 12.4 YPC, 4.5% TD/tgt, 9% PD/INT per tgt
Harmon = 10 tgts (3.0% of snaps), 60% comp, 13.7 YPC, 10% TD/tgt, 20% PD/INT per tgt
DMac = 18 tgts (3.8% of snaps), 78% comp, 10.3 YPC, 28% TD/tgt, 5.6% PD/INT per tgt