KJ Duff is a massive possession X receiver whose grade is built on size, catch radius, ball tracking, contested-catch production, and red-zone value. He wins best along the boundary, where he can box out smaller corners, work intermediate windows, and create quarterback-friendly targets without needing elite separation. The concern is whether his release package, route suddenness, YAC ability, and blocking physicality become good enough to hold up against NFL press coverage. His next-tier jump depends on proving he can separate more consistently, not just win through contact.