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Three of the greatest running backs of this generation switched teams in recent weeks, with Jamaal Charles, Adrian Peterson and Marshawn Lynch donning new uniforms. But history says that when a great running back’s longtime club says it’s time to say goodbye, the team is usually right.
Since the 1970 AFL-NFL merger, 10 Hall of Fame backs have switched teams at age 30 (though Earl Campbell was actually traded at age 29). None gained…