Former Pittsburgh Steelers defensive lineman L.C. Greenwood waving to fans in 2006. He died Sunday at the age of 67. Stephen M. Gross /UPI /Landov hide caption

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The Michigan Wolverines defeated the Notre Dame Fighting Irish Saturday night, 41-30 — and then celebrated by playing some polka. Here, the Irish's Chris Brown is tackled by Michigan's Delonte Hollowell after making a catch. Gregory Shamus/Getty Images hide caption

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Tim Tebow (right) shakes hands with New England Patriots quarterback Tom Brady after the Patriots defeated the Broncos on Dec. 18, 2011. Now, they're due to be teammates. Mark Leffingwell /Reuters /Landov hide caption

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Eric Fisher, offensive tackle from Central Michigan, was the No. 1 pick in the 2013 NFL draft. He was chosen by the Kansas City Chiefs. Rich Kane /UPI /Landov hide caption

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Oklahoma quarterback Steve Davis, left, and coach Barry Switzer celebrate the team's No. 1 ranking after the Orange Bowl in 1976. Davis, 60, died Sunday in the crash of a small plane. Switzer called Davis a "great role model for young people." /AP hide caption

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The brain of former NFL star Junior Seau, who committed suicide last year, showed signs of the kind of neurodegenerative disease associated with repetitive head trauma. Elsa/Getty Images hide caption

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Linebacker Ray Lewis announced Wednesday that he will retire after the Baltimore Ravens' season ends. Most media coverage of Lewis' legacy has omitted his part in a 2000 double-homicide case. Harry How/Getty Images hide caption

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Andy Reid as he left the field Sunday in New Jersey. His last game as head coach of the Philadelphia Eagles was a 42-7 loss to the New York Giants. Elsa/Getty Images hide caption

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Dr. Ann McKee, professor of neurology and pathology of Boston University School of Medicine and co-director of the Veterans Affairs Center for the Study of Traumatic Encephalopathy, inspects a brain in the Bedford Veteran Medical Center last year. Stan Grossfeld/Boston Globe via Getty Images hide caption

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Denver Broncos Coach John Fox yells at field judge Jimmy Buchanan during the Broncos' game against Atlanta Monday. Referring to the game, the NFL insisted that players and coaches give replacement referees, and the game, more respect. Kevin C. Cox/Getty Images hide caption

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