Sarah Johnson makes a call during the first half of an April 2014 preseason NFL football game between the Seattle Seahawks and the San Diego Chargers. Stephen Brashear/AP hide caption

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Sarah Thomas calls holding during a preseason game between the Oakland Raiders and New Orleans Saints in 2013. Michael Democker/The Times-Picayune/Landov hide caption

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San Francisco 49ers linebacker Chris Borland, center, during an NFL football game in Santa Clara, Calif. Borland announced that he will retire after just one season to protect himself from brain injuries. Marcio Jose Sanchez/AP hide caption

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San Francisco 49ers linebacker Chris Borland (50) is seen here in a game last year against the New York Giants. Borland, who had two interceptions in that game, has announced that he is retiring from the NFL after his rookie season. Chris Szagola/CSM/Landov hide caption

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Fans hold a "Los Angeles Rams" sign during a San Diego Chargers game against the St. Louis Rams last year. Both teams are part of proposals to build new NFL stadiums in the LA area. Donald Miralle/Getty Images hide caption

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Leland Melvin with his dogs, Jake and Scout. "I snuck them into NASA to get this picture," Melvin says. Courtesy of Leland Melvin hide caption

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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

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

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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

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

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Tom Brady of the New England Patriots hands the ball off to LeGarrette Blount during the AFC Championship Game. The Patriots are being investigated because of game balls that were improperly inflated. Elsa/Getty Images hide caption

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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

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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

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A deflated football would have been easier for New England Patriots quarterback Tom Brady (12) to grip in Sunday's rain. Charles Krupa/AP hide caption

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Questions over out-of-regulation footballs have come up after the New England Patriots won the AFC Championship Game Sunday. Running back LeGarrette Blount ran for 148 yards and three touchdowns in the Patriots' 45-7 win over the Indianapolis Colts. Elsa/Getty Images hide caption

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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

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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

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