The scowl became part of American soccer. Fixed across Heather O'Reilly's face each time she sped toward the end line and curled her foot around a cross, it seemed to neither age nor change.
As O'Reilly grew from a teenage phenomenon into a veteran who this week will retire from the national team after 231 appearances, the scowl was so familiar it was almost comforting.
So it was that as the national team escaped its own adolescence this century, O'Reilly was a constant.
Aging because we all do. Changing because a player must. Somehow always comfortably familiar.
And if it is no longer difficult to imagine what the national team will be on the field without her, it will be forever difficult to picture the events of the past decade and a half unfolding sans scowl.
Except that, when you get right down to it, labeling hers a scowl seems barely sufficient.
University of North Carolina coach Anson Dorrance -- the architect of the most prolific dynasty in college sports who watched so many former Tar Heels first debut for and eventually retire from the U.S. women's national team -- offered a better appraisal.
"What sort of made her fierce was this angry chicken face that she had when she competed," Dorrance said.
Beyond the field, though, there was a smile with a hint of native New Jersey wryness.
"There's no arrogance to her," Dorrance continued. "She would not call a team that defeated her a collection of cowards. There are so many things about her that are genuinely good and nice. She's just a very old-school athlete that loves her family, loves her teams and her coaches, and isn't this incredibly irritating social media presence. It's almost like she is from a different era."
Mind you, irritating or not, she does have a social media presence. O'Reilly's combined Twitter and Instagram followings are more than half a million strong. She is of this time. But the coach's point is taken. It never has been easy to pin down the era to which she belongs. Perhaps it is her own.
O'Reilly will retire from international competition after Thursday's match against Thailand (ESPN2, 8 p.m. ET) having played more games for the United States than all but six women. At 31, she is 2½ years younger than one U.S. captain, Carli Lloyd, and only six months older than the other, Becky Sauerbrunn. And while O'Reilly was an Olympic alternate this summer in Brazil, she still plays with the skill of someone who has a lot of soccer left in her story.
Dorrance said he turned on an NWSL game last week just in time to see O'Reilly, of FC Kansas City, "carve" Chicago Red Stars defender Julie Johnston, a U.S. teammate and rising star, and deliver a cross that Kansas City's Shea Groom finished for the opening goal in a K.C. win.
In other words, the kind of play O'Reilly has been making ever since she made her international debut against Sweden on March 1, 2002 -- three days before Groom's ninth birthday.
But with last year's World Cup championship medal sitting alongside three Olympic gold medals, and with three long years until the next major tournament -- not to mention the national team's undisguised youth movement, to which O'Reilly fell victim this year -- she makes her exit.
"As much as I would like to play in the national team until I'm 80 years old, that's just not realistic," O'Reilly said. "There are other amazing things I'm looking forward to as well. I'm genuine about this -- I'm looking forward to being a fan and being behind this team forever and ever because it's part of me and always will be."
And she is a part of it. Not just because of 52 assists. Not just because of 46 goals, including a memorable winner in overtime of an Olympic semifinal against Germany in 2004. Not merely for the gold medal that followed or any of the other medals added later. She played her first game alongside Joy Fawcett, Julie Foudy and Kristine Lilly, all of whom played in the first World Cup in 1991. She will play her final game alongside some combination of Morgan Brian, Lindsey Horan and Mallory Pugh, some of whom might still be playing when the 2031 World Cup rolls around.
That is a whole lot of history connected through one person.
Most of O'Reilly's career took place in that most difficult of historical settings, when the glow of something momentous -- in this case, the national team's culture-changing success in the 1996 Olympics and 1999 World Cup -- gives way to the arduous task of making a new reality stick. That is why it matters when she says she feels that she leaves the national team in better shape than she found it.
"I think being a professional soccer player is the coolest gig in the world; I love playing," O'Reilly said. "I think sometimes when you look at our male counterparts and what they are able to do in a domestic league and certain international players, we certainly have a ways to go. So yeah, that's frustrating. And I'm proud to be part of certain initiatives to level that playing field because we're not there yet. Hopefully I will continue to be a positive person in that charge to make things more equal, in terms of conditions, in terms of pay, in terms of visibility of the sport."
Although she has been one of the most thoughtful speakers on rosters that rarely lacked candidates in that category, O'Reilly isn't the first name that comes to mind when it comes to using the platform. That is our fault, not hers. We digest and discuss Megan Rapinoe kneeling during the national anthem because it is, by intent, visible and provocative. We hung on Abby Wambach's every spoken thought for the same reason.
How many fewer words, as absent here as anywhere, have been devoted to the work O'Reilly quietly does with America Scores, among others? The nonprofit organization works with children in 13 major cities who almost exclusively live below the poverty line. Through soccer, but also community service and even poetry, it attempts to provide opportunities that might not otherwise exist in a sport still very white, suburban and expensive.
"I think that soccer is a powerful game," said O'Reilly, who graduated from North Carolina with a degree in education. "It's changed my life, and I know that it has the power to change the lives of a lot of people. And I don't know if everybody across our country is getting the same access to this amazing game."
She was among those heard on the subject of artificial surfaces in the most recent World Cup. She believes in the ongoing fight for wage equality. But her career is also a study in the idea that it is not always the loudest and the brashest who make the biggest difference.
For 15 years and more than 200 appearances, she didn't try to be anything but herself. The angry chicken face is just the photographic proof.
"At first I was sort of embarrassed by when I'd see pictures," O'Reilly said. "Over the years I've just embraced it because it's who I am. I play with passion. I live with passion. I'm proud of that. I feel like that's what made me successful in my career. And I don't know another way."