When the Patriots traded Duron Harmon to the Detroit Lions last season, they never really brought in his replacement. For a team that likes to use a three-safety set with two guys deep, the second free safety role is key. However, last year that role was filled almost exclusively by cornerbacks playing out of position. With Harmon now a free agent, the Patriots could bring him back and plug him into his old spot next to Devin McCourty. It’s not a strong year for free safeties in the draft or free agency, and Harmon will likely come cheap and with prior knowledge of the system.