Malcolm Butler (right) of the New England Patriots intercepts a pass intended for Ricardo Lockette of the Seattle Seahawks late in the fourth quarter of Super Bowl XLIX on Sunday. Timothy A. Clary/AFP/Getty Images hide caption

itoggle caption Timothy A. Clary/AFP/Getty Images

Football rules, uniforms, helmets and protective gear have changed a lot over the years. Keystone-France/Gamma-Keystone via Getty Images hide caption

itoggle caption Keystone-France/Gamma-Keystone via Getty Images

Bill Parcells has been coach to the Dallas Cowboys, the New York Giants, the New England Patriots and the New York Jets. Robert B. Stanton/Getty Images hide caption

itoggle caption Robert B. Stanton/Getty Images

Rafael Nadal (right) shakes hands with Tim Smyczek after winning a match at the Australian Open on Jan. 21. Rob Griffith/AP hide caption

itoggle caption Rob Griffith/AP

High school athlete Graham Hill, number 50, suffered a concussion in 2013 while playing football at Trinity Christian Academy in Addison, Texas. Courtesy of Jeffrey McWhorter hide caption

itoggle caption Courtesy of Jeffrey McWhorter

New England Patriots head coach Bill Belichick speaks during an NFL football news conference at Gillette Stadium, on Saturday in Foxborough, Mass. Belichick defended the team against allegations they had cheated by using underinflated footballs in a championship game. Steven Senne/AP hide caption

itoggle caption Steven Senne/AP

New England Patriots head coach Bill Belichick, seen here on Jan. 18, says he "had no knowledge" about the controversy over deflated footballs "until Monday morning." Elise Amendola/AP hide caption

itoggle caption Elise Amendola/AP

Panelist Nahshon Ellerbe, a star running back at Trinity Christian Academy in Addison, Texas, warms up before a game against Midland Christian. Jeffrey McWhorter/Trinity Christian Academy hide caption

itoggle caption Jeffrey McWhorter/Trinity Christian Academy

The Army-Navy game on Dec. 7, 1963, was the first televised sports game featuring instant replay. Its inventor, Tony Verna, died Sunday at 81. AP hide caption

itoggle caption AP

Boyd Dowler of the Green Bay Packers grabs a Bart Starr touchdown pass in the NFL championship game on Dec. 31, 1967. The "Ice Bowl," played in frigid temperatures, was won by the Packers 21-17. AP hide caption

itoggle caption AP

The Yale football team in an undated photo. Commentator Frank Deford finds it curious that a sport as brutal as football became popular among the academic elite. AP hide caption

itoggle caption AP

Inside the control room, dozens of monitors allow the production team to keep an eye on the live games and the available replays and graphics. Becky Sullivan/NPR hide caption

itoggle caption Becky Sullivan/NPR

Making and taking a hit chest to chest, instead of skull to skull, is easier to remember if you're not wearing a helmet, say University of New Hampshire Wildcat football players. Jack Rodolico/New Hampshire Public Radio hide caption

itoggle caption Jack Rodolico/New Hampshire Public Radio

FIFA President Joseph Blatter is flanked by Russian Deputy Prime Minister Igor Shuvalov (right) and Qatari Emir Sheikh Hamad bin Khalifa Al-Thani on Dec. 2, 2010, in Zurich, Switzerland, after the announcement that Russia will host the 2018 World Cup and Qatar in 2022. Michael Probst/AP hide caption

itoggle caption Michael Probst/AP

Go Big Green! Dartmouth is testing the VGo robot to help diagnose concussions when neurologists aren't at the game. Mark Washburn/Courtesy of Dartmouth-Hitchcock hide caption

itoggle caption Mark Washburn/Courtesy of Dartmouth-Hitchcock