NFL parity, an unforgiving 17-game schedule, and the constant threat of injuries make a perfect regular season extraordinarily difficult. No team has finished 17-0 since the 1972 Dolphins went 14-0, and even strong contenders in recent seasons—such as the 2025 Eagles and Bills—saw undefeated streaks end by Week 5. Top projected squads like the Chiefs, Ravens, and Rams face stacked divisions, divisional rivals with comparable talent, and quarterback or key roster health risks that historically derail momentum. Trader consensus at 91.5% against reflects this combination of historical precedent, league-wide depth, and the narrow margin for error across a full slate of games.