Justine Henin stunned the tennis world on May 14, 2008 by announcing that she was retiring while she was the world No. 1. The decision abruptly ended the career of the top-ranked WTA player at the time and became one of the sport’s biggest off-court shocks. It mattered immediately because the women’s tour lost its No. 1 mid-season, forcing a sudden reset at the top of the game.