SCOTT DETROW, HOST:
Headers make for some of the most exciting moments in a game of soccer.
AILSA CHANG, HOST:
They're fast-paced, unpredictable plays that can shake things up when a match is getting desperate.
BRENNAN KLEIN: This level of uncertainty that you can inject into the game, that might be all you have.
CHANG: Brennan Klein says that's never been truer than at this year's FIFA World Cup.
DETROW: Wednesday, Argentine striker Lautaro Martinez used his head to knock in a Lionel Messi cross in the semifinal against England in the 92nd minute to win the game.
CHANG: But new research from Klein's team at the Network Science Institute at Northeastern University has found that the role of headers in the international tournament has changed.
KLEIN: What we're noticing is that the percent of goals that are scored with the player's head has been decreasing steadily, and it's at its lowest point right now.
DETROW: Klein says this decline is, in part, a strategy shift. As defensive strategies have been getting better, it's harder to just head a ball into the goal, so players are more selective.
KLEIN: It's actually worth it to not head the ball unless I know I'm going to have an accurate on-target header.
DETROW: Klein says the data show the strategy is paying off.
KLEIN: It's this two-sided coin. So on the one hand, the percent of goals scored with the player's head is decreasing. But those goals that are scored are higher expected goal chances.
CHANG: So don't worry, soccer fans, you might be seeing fewer headers, but the headers you do see will be more likely to produce goal-scoring plays that you will remember.
DETROW: Klein says a good way to think about this is that fans are witnessing soccer evolving in real time.
KLEIN: Headers are a good example of one area of the pitch where tactical innovations are really driving responses.
DETROW: Klein says that the concerns shaping the future of World Cup headers aren't just about strategy.
KLEIN: A lot of header-related injuries have popped up in recent years, and these are quite serious, and we're still starting to understand the true extent of their severity.
CHANG: Around the world, youth soccer clubs are banning headers for younger players that might be affected more severely by those cranial collisions.
KLEIN: And this is a deliberate choice by parents, by coaches and by governing bodies. The sport is trying to intervene.
CHANG: While FIFA has not imposed any ban on headers, a generation of professional players coming up under the changed youth club rules will be more likely to stick to their feet.
KLEIN: In 10, 15 years, we'll start to see a nuanced style of play that doesn't rely on these headers for getting goal-scoring opportunities as a direct result of our increased knowledge of how dangerous these can be.
DETROW: So it's not quite time to say goodbye to this iconic soccer move, but styles of play are always changing, and it's hard to know just where the future is - hmm, hmm, hmm (ph) - is headed.
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