Nobody knows when the NFL will play its next game. The owners have locked out the players, and part or all of the 2011 season could be lost.

We have a pretty good idea of what the NFL’s next play will look like, however. A kicker will boot the ball from the 35-yard line, most likely for a touchback. That’s because on March 22, the NFL changed the rules, moving kickoffs forward from the 30-yard line. It hopes to reduce the risk of injury during what is often the most harrowing play — enormous men colliding in an open field at full speed, like beat-up cars in a high-stakes demolition derby.

Football has fallen under intense scrutiny for its violence — not just for the immediate injuries that players can endure on the field, but also for the long-term health effects that the game may have on cognitive performance. Research indicates that NFL veterans are uncommonly prone to dementia.

History is repeating itself. For whatever issues football has today, they are nothing like the controversy it experienced a little more than a century ago. Back then, injuries were an afterthought — it was the deaths that concerned people. In 1905, there were 18 of them, occurring everywhere from the college gridiron to neighborhood sandlots.

Horrified by the slaughter, a group of progressives crusaded to ban football. They formed a social and political movement whose ranks included the renowned Harvard President Charles W. Eliot, frontier scholar Frederick Jackson Turner, aging Confederate Gen. John Mosby and muckraking journalists.

The Nation magazine worried that colleges were becoming “huge training grounds for young gladiators, around whom as many spectators roar as roared in the [Roman] amphitheatre.” After watching a college game in 1903, one writer condemned what he saw: “The dirty players in football are the thugs of society, and the disgrace of the university that tolerates their presence on the team.” The New York Times fussed over football’s trend toward “mayhem and homicide.” About two weeks after printing these words, the Times ran a new editorial. The headline was “Two Curable Evils.” The first evil it addressed was the lynching of blacks. The second was football.

Yet the sport had at least one very important fan on its side — President Theodore Roosevelt.

Roosevelt attended his first football game in 1876, as an 18-year-old Harvard freshman. He and a group of classmates took a train from Cambridge, Mass., to New Haven, Conn., where they took in the second-ever football game between Harvard and Yale, in what has since become a storied rivalry. Harvard lost that day, but the sport hooked the young adventurer.

Roosevelt never played football himself — he was too small and wore glasses — but he enjoyed it and believed it served a useful social purpose. By turning boys into men, it prepared the United States for the challenges of a new century.

In 1905, with football’s violence becoming impossible to ignore, he summoned the coaches from Harvard, Princeton and Yale to the White House and encouraged them to reform the game.

That winter, they created the organization that became the NCAA and invented the forward pass — a revolutionary rule change that separated the sport from its rugby-like origins and made it a uniquely American game loved by millions today. Before the pass, football was a glorified contest of pushing and shoving as men battled over small gains and often slugged each other beneath their frequent pile-ups. Afterward, play spread across the whole field. Size still mattered, but so did fleet-footed dexterity. Within a few years, the fatalities subsided.

Even if the progressives had not succeeded in banning football, their campaign could have marginalized the game, condemning it to a future of limited appeal, along the lines of lacrosse. Roosevelt’s intervention may have saved football from this sorry fate.

Today, many parents encourage their children to play sports because these activities improve fitness, stress teamwork and build individual character. Roosevelt believed athletics accomplished all of these things as well — and he had the gumption to stand up for a rough game when it came under fierce assault.

Late in life, Bill Reid, who had attended the White House football summit as Harvard’s coach, reflected upon what had happened: “You asked me whether President Theodore Roosevelt helped save the game. I can tell you that he did.”

John J. Miller is national correspondent for National Review and author of “The Big Scrum: How Teddy Roosevelt Saved Football” (Harper), out now.