Spikes' low broken tackle rate can be attributed to one significant point; he was primarily played as a two down run stuffer who could bring the heat. The counterpoint to that is, in the passing game, teams would abuse Spikes by targeting his assignment knowing he didn't have the speed to play pass coverage.
If the Patriots can somehow land someone such as Ryan Shazier, Telvin Smith or Jordan Tripp then I would be pretty happy with a unit of Mayo, Hightower, Collins and a draft pick. From there, it's adding depth that will be the key.