The Patriots have two Pro Bowl caliber linebackers in Dont'a Hightower and Jamie Collins. I believe the Patriots will find a way to extend both their contracts given how important they are to the defense. However, they must also have a plan ready in case Plan A fails. Ideally who they draft can play the 3rd linebacker role and contribute on Special Teams in Year 1 while being able to step up to a starting linebacker role in Year 2 as part of a rotation or as a replacement in case either LB walks in free agency.
Joshua Perry: Perry is overshadowed by teammate Darron Lee, who will likely be a first round pick in this draft, but can offer the Patriots a lot of value in the 2nd. Perry is very steady at everything, whether it's filling in holes in run defense, tackling, covering, or blitzing. That type of versatility appeals to a team like the Patriots, who find creative ways to utilize their linebackers. Perry is built similar to Jamie Collins at 6'4" 253 and 33 1/4" arms. The only issue I see with Josh Perry and the Patriots is whether Perry is on the board long enough for the Patriots to get him. In Year 1 he should be a 3rd linebacker and play on Special Teams as he waits his turn on defense. Perry will not finish Senior Bowl week after sustaining a groin injury.
Kentrell Brothers: Brothers is a bit shorter than Perry at 6'1" 249, but he fulfills the Patriots size requirement at LB. Brothers has sideline to sideline range, racking up 150 tackles and 2 INTs. Brothers is on the fringe of being a first round pick in the draft and a solid Senior Bowl will solidify him as a first rounder. The only way the Patriots likely get Brothers is if something bad happens to him and he falls down the board.
There are other potential prospects that can fill in like Tyler Matakevich. The only concern I have with Matakevich is size related, as he weighed in at 6'0" 233. Now that doesn't mean he can't be a possible depth option but I have serious doubts about him starting on this defense as he'll need to play behind a strong DL that can keep blockers off of him. Matakevich could be a strong late round value as a depth/ST player.