At Flushing Meadows, one of sport's most enduring figures walked off a Grand Slam court for perhaps the last time, undone not by a rival's brilliance alone but by a body that could no longer honor the will behind it. Novak Djokovic, 39, fell to Argentine Mariano Navone in five sets across nearly five hours, suffering his earliest major exit in two decades and raising the quiet, heavy question of whether greatness has finally met its limit. The match was less a defeat than a reckoning — a reminder that even the most disciplined human machines are still human.