Competition is the name of the game in sports. But without a doubt, the fiercest battles are fought when longtime rivals come face-to-face. Here are in-depth looks at five of these legendary rivalries: Yankees vs. Red Sox, Celtics vs. Lakers, United vs. Galaxy, Canadiens vs. Bruins, Bears vs. Packers. Find out what sparked the feuds, and get insights into the heated clashes that turned opponents into bitter enemies. Don't miss the classic moments and play-by-play game action!