League vowed this off-season to take steps toward protecting players who suffer concussions on the field, ranging from establishing a whistle-blower hotline to giving team doctors final say over who can play and who can’t.

But while getting serious about treating concussions is a laudable goal, there’s just one problem: Most players don’t want to be protected.

Detroit Lions quarterback Jon Kitna is the latest NFL player to show why the culture of professional football makes it difficult if not impossible to prevent players from playing after they’ve suffered concussions during games. Early in the second quarter of the Lions’ game against the Minnesota Vikings Sunday, defensive end Ray Edwards drilled Kitna from behind, and he got up woozy. Kitna stayed in the game for the rest of the drive (which ended when he threw a touchdown pass), but when he went to the sidelines, the Lions’ medical staff diagnosed him with a concussion.

Kitna was replaced by backup quarterback J.T. O’Sullivan, but as O’Sullivan struggled and it became clear that the game would go down to the wire, Kitna said he felt fine and began to lobby the team’s medical staff to clear him to return to the game. Eventually, the Lions’ doctors acquiesced, and Kitna led the team to an overtime victory. In the celebratory postgame locker room, his teammates and coaches described him as heroic.

Kitna, who has suffered two other concussions in his NFL career, said after the game that Sunday was “the worst my head has ever felt” and added that he “barely” knew where he was. His teammates said afterward that Kitna had trouble remembering things, couldn’t focus, and was bothered by bright lights. And yet he insisted that it was the right decision for him to return to the game, even though he got hit several times in the fourth quarter and overtime, including three different runs when he had the opportunity to slide or run out of bounds but instead lowered his head in an effort to pick up extra yards and absorbed shots from Vikings players.

Neurologists are nearly unanimous that athletes who suffer concussions during sporting events should not return during the same competition, and many doctors have criticized the NFL for taking a cavalier attitude toward concussions. People who have concussions are at an increased risk of future medical problems ranging from memory loss to headaches to depression, and a number of former NFL players have said that concussions they suffered on the field have dramatically reduced their quality of life in retirement. Notable players including Hall of Fame quarterbacks Troy Aikman and Steve Young, as well as former Jets receivers Wayne Chrebet and Al Toon, had their careers cut short by concussions.

The NFL’s policies on concussions have drawn increased scrutiny in recent years, and the league announced this off-season that medical personnel — not players or coaches — would have final say over whether a concussed player could return to a game. The league also distributed a telephone number to every NFL player, coach, trainer, and team doctor asking them to report teams that pressure players to play when they’re suffering from the effects of a concussion. Kitna, however, showed that while this policy sounds good in theory, it is nearly impossible to manage in practice. If a player insists that he’s feeling fine and ready to play, and if a coach says he needs the player on the field for the team to win the game, will the team’s medical staff really hold the player out?

And do the players even support the policy that’s designed to protect them? Sometimes when the medical staff does its job by protecting the players, the players are angry about it. Last week, San Diego Chargers kick returner Darren Sproles suffered a concussion on the opening kickoff of the season and was furious when the team’s medical staff wouldn’t clear him to return to the game. The next time Sproles takes a hard hit and comes up feeling dizzy, he might just tell the medical staff that he feels fine and keep playing. Concussions are difficult to diagnose, and if the players are hesitant to cooperate with the team doctor for fear that they’ll be held out of the game, there isn’t much the doctor can do.

Ultimately, the NFL players’ union may be the organization most responsible for protecting players from the long-term effects of on-field concussions. After all, there isn’t a much more fundamental purpose of a labor union than ensuring the safety of its membership. But the NFL Players Association hasn’t made preventing concussions a major issue. When the union and the owners negotiated a new collective bargaining agreement last year, the major issue was player salaries, not player safety.

Still, although attitudes toward concussions are changing slowly, they are changing. As he discussed Kitna yesterday, the 58-year-old Lions coach Rod Marinelli was asked how many concussions he suffered as a college football player.

“Never counted,” Marinelli said. “Nobody cared.”

Mr. Smith is a writer for FootballOutsiders.com.