Kyle Van Noy, Jamie Collins, and Elandon Roberts are all free agents and the New England Patriots defensive dominance is in serious jeopardy.
There is a very good possibility that the Patriots are going to lose both Kevin Van Noy and Jamie Collins. Most years that would send Pats Nation into a panic, but the Patriots are in a position that they can afford to lose them and continue performing at high levels. But, very similar to the offensive line the linebacking corps will turn into a house of cards.
The best case scenario is that the Patriots can secure Jamie Collins at an affordable price. Collins play last season probably dictates that he's due a pay raise, but Collins has made significant money throughout his career while he was with the Cleveland Browns, and there is an outside chance that Belichick could convince him to stay with the Patriots and try to add a second Super Bowl ring to his collection. If the Patriots were able to secure Collins, it would add the depth the Patriots need.
Kyle Van Noy is as good as gone. Van Noy indicated that he would like to stay with the Patriots, but coming off a career year, he's heading into free agency and there are a lot of teams with a lot of money to spend. It wouldn't surprise me at all if he ended up with either the New York Giants, Detroit Lions, or Miami Dolphins, three teams with Belichick disciples as head coaches.
Elandon Roberts is also a free agent, but that's the one piece I feel the most comfortable that the Patriots will be able to re-sign.
If the Patriots lost Collins and Van Noy, but we're able to keep Roberts, that would leave the Patriots with Dont'a Hightower, Ja'Whaun Bentley, and Elandon Roberts. Belichick could fill in the rest of the depth chart with draft picks and lesser free agents. That's a good three man core, but an injury would send the whole thing into a tail spin.
There are questions around the Patriots defensive line, but the "Boogeymen" were able to make up for the line, and the way things are shaping up it looks like they'll be relied upon just as much, with not as many weapons. An injury would leave the Patriots defense in a bad spot and would all but eliminate the pass rush.
A linebacker who is NFL ready has to be a priority for Belichick in the draft, otherwise there are reasons to be worried about the Patriots defense next season.