IT'S 10 MINUTES before practice in the Chicago Red Stars' training room, and midfielder Julie Ertz is curled up on a massage table, cupping the arches of her feet. She suctions her skin into a small, pressurized globe, a process that calls to mind medieval torture but allegedly relieves tightness. Her toenails are painted periwinkle blue. A small cross tattoo is tucked behind her ear like a flower.

Ertz winces as she pops the seal of skin, then hops off the table and runs the tender pockets of her feet over a golf ball. She has high arches, a foot shape better suited to ballet than soccer and one that causes her intense discomfort every time she hits the pitch.

"I was 23 in the last World Cup," the team captain says matter-of-factly. "Now I need to listen to my body more."

On the floor, various teammates receive their own treatments: icing knees, heating quads, feet submerged in buckets soaking ingrown nails. They chat amiably about the dubious sartorial cred of Uggs, big versus small dogs, new restaurants, Gossip Girl -- the free-flowing, unconcerned conversation found in groups with decades of shared history and unambiguous commonalities. Every few minutes, forward Michele Vasconcelos' toddler, Scarlett, is rolled through the room in a plastic pushcart, a small soccer ball bouncing in the front.

"It was fire," Ertz shares about the foosball tourney she and a few other players got into last night, noting, "I made Gilly [Arin Wright, née Gilliland] switch positions because she wasn't defending well enough." Ertz laughs, says she had no skin in the game beyond "you know, pride."

Soon, the players hit the field and begin running laps. They shift like a flock of geese, repositioning en mass, pivoting to and fro as if nudged by the wind. During drills, Ertz transforms. She yanks her ponytail tight, walks the turf with a purpose, bowlegged, arms bent and floating at her hips like a cowboy ready to draw. Her expression is serious, contemplative, her genial demeanor subsumed by the beast within.

"I'm the kind of person that wants to take advantage of all my opportunities," she explains. And for Ertz, practice is as critical an opportunity as any.

Capitalizing on her prospects is something the seasoned defensive champion has been doing since her teens. After a winning stint at Santa Clara University, the NWSL rookie of the year became the second-youngest player on the victorious 2015 World Cup team, a position she slid into after an injured Crystal Dunn was dropped from the roster. Former alternate Ertz seized her moment by the throat, playing every second of the tournament, emerging as a star.

In 2017, she was named U.S. Soccer Female Player of the Year, and she is now viewed by many as the most critical component in the projected success of the 2019 national team -- the strategic linchpin and a player head coach Jill Ellis describes as "a weapon" who "will run through anything."

Like the Kool-Aid Man, Ertz has a reputation for furiously demolishing barriers with a smile. On the outside, she is all warm, sunny blond; on the inside, it's Game of Thrones, mother of dragons. She has etched her place in soccer history as a rare amalgamation of physical and technical threat, the uncommon defender who dissects film and tackles audaciously, her body as ruthless as her brain.

"Julie is incredibly intelligent about the game," Chicago head coach Rory Dames says. "She's like having another coach on the field."

Dames drafted Ertz to the Red Stars five years ago, in large part because of her brute chutzpah. "Julie puts her body on the line. It's unusual to have a player that has all the characteristics that Julie has and still have her willingness to tackle," he marvels, adding, "There is no gray area for her."

Teammates describe Ertz as a player who thrives under pressure, joyfully running headlong into the mouth of every cannon.

"Julie is probably one of the more aggressive players that we have," says keeper Alyssa Naeher, who plays alongside Ertz on the USWNT and the Red Stars. "She's the one that's going to the ground. Which is weird because off the field, you don't see that side."

Out of uniform, Ertz, 27, is chill, open, thoughtful. She makes a lot of deep eye contact. She keeps her indulgences in check. She does not smoke or drink or eat crappy food or sleep late or skip practice. She's like Sandra Dee, if Sandra Dee possessed a secret, bone-deep desire to knock your punk ass into the artificial turf.

"If her goal was just to be a great soccer player, that goal would've already been accomplished," observes her husband, Philadelphia Eagles tight end Zach Ertz. "She could rest on her laurels and be complacent. But she's not."

Julie Ertz is the opposite, consumed by self-scrutiny, poking at what she perceives as her weak spots like a tongue prodding an aching tooth.

"When you fail or you make a mistake, you learn a lot about yourself," she explains. "That wouldn't happen if I just did everything right. You know what I mean?"

"Julie was always there to push me," says Ertz's sister, Melanie. "She would tell me putting in a mediocre effort wasn't good enough." Mary Ellen Matthews for ESPN

IF YOU ASK her, Ertz will tell you she doesn't have nightmares. She dreams nearly every night. But her head is filled instead with happy fantasies and memories. Sometimes she dreams about past vacations or trips to the sea. More often, she dreams of soccer.

"I see moments of a game that could happen," she says, knitting her brow. Premonitions and "visions," not of trophies but of plays, of tackles. Even at rest, she is strategizing.

Ertz sees nothing odd about this. The infinite calculus of soccer has been her abiding preoccupation since she was an eager child in Mesa, Arizona, stumbling into a lifelong passion while trying to beat her two-years-older sister, Melanie, at something, anything. (Ertz's grandmother remembers Julie making up rules to win at Candy Land.)

Natural athletes, the sisters were encouraged to battle. Their father, David Johnston, a starting kicker for LSU, designed makeshift physical challenges to entertain them whenever he could. Chores became races. An idle jump on the trampoline transformed into a contest to see which daughter could jump higher over a swinging pipe.

David worked in the cold room at Shamrock Foods, lifting heavy stock 65 hours a week. Mom Kristi was a nurse. The family bedrock was hard work and the belief in its ability to cement character.

"It was tough love," Ertz recalls.

"My dad wanted us to find that drive at a young age," Melanie says. "The mentality was, 'No one is stopping you but yourself.'"

1999 Women's World Cup Watch "espnW Presents: The '99ers, Reunited" at 7 p.m. ET May 16 on ESPN2. Julie Foudy joins 1999 Women's World Cup USWNT teammates Mia Hamm, Michelle Akers, Briana Scurry, Kristine Lilly and Brandi Chastain for a roundtable discussion about their historic victory, their memories from that year and the legacy they left behind. Watch a sneak peek.

The two girls shared a room, an enforced closeness that Melanie says brought benefits -- "We were partners in crime" -- and annoyances -- "Julie borrowing my Hollister T-shirt, not hanging it up, it's on the floor types of things."

The sisters excelled in every sport but showed particular promise in soccer, a game "my parents didn't know anything about," Ertz recalls. By age 9, Ertz thought of little else. Local leagues were joined. A net was erected in the backyard. Self-motivated practice was expected. If this was where the family time and money was going to be spent, the girls were called upon to take their commitment seriously. Ertz says the early accountability was a blessing.

"It made us super independent. Our parents made it known, we're going to treat you like an adult."

David and Kristi logged extra shifts to pay for team expenses. The girls' heavy sporting schedule meant cheap pizza dinners in the car, hours commuting to matches every weekend. There were no vacations that didn't revolve around soccer.

"That's why Julie and I are so hard on ourselves to perform at a higher level," Melanie says. Neither child wanted the sacrifices their parents made to be for nothing.

Whenever Melanie joined a league, Julie followed. After a growth spurt in middle school, Julie began eclipsing her sister on the pitch. "Julie was so advanced. She played above her age," Melanie recalls.

At 13, Ertz switched to a more hard-core club with European coaches, and the die of her career was cast. "I loved how seriously everyone there took it," she says -- her most of all. It was a fevered dedication that's only grown over the ensuing dozen years, Ertz sewing up a heady college run before dropping out to go pro in 2013, a decision that haunts her slightly.

"I wanted to finish, and I really, really tried," she says. "It was hard to balance classes while I was getting called in with the national team. My parents still ask me when I'm going to finish my education, and I tell them, 'Soon.'"

When asked why she would bother at this point, Ertz says flatly, "To say I did it."

She is a completionist. "I want to win more games," Ertz says of her immediate goals. "I will never be satisfied," she says of her competitive mentality. "It's such an honor to be able to represent your country that I just don't ever want to let it down."

"Julie is a sore loser," Zach confides with a chuckle. "If I beat her at something, I try to keep it mellow because I know the repercussions if I go all out."

Julie does not disagree.

"I want to be a good, moral person and have good values," she says earnestly. "But I don't think I'll ever mature about how to act about losing. I hate losing so much."

Ertz is happiest with her husband. (The soccer field, she says, is a close second.) Her call log reads like a skipping record. Hubby, hubby, hubby, hubby, hubby FaceTime, hubby FaceTime, hubby.

The two famously met at a Stanford baseball game, him quiet, her chatty. They shared sunflower seeds. A friendship developed. Six months later, they were an item, bonding over their willingness to forgo late nights on the quad for a pursuit of athletic excellence, a commitment unusual among their peers. Zach also reminded Julie of her father: reserved, with a well of sweetness beneath the surface. She knew it was serious when the two of them could drive in silence and not feel awkward.

Julie took Zach home, the first boyfriend to meet her parents. It was July in Arizona. Sweltering. "He was absolutely miserable," Julie remembers, laughing.

Adding to the discomfort, the family Johnston is a "more the merrier" extended dance remix crew, the sort that gathers every aunt, uncle and second cousin together any chance they get; boisterous, voluble -- at least on the maternal side. When Zach was introduced to the cheerful chaos, "he was like, 'This is insane!'" Julie recalls. "He was really nervous."

Since then, "Julie has pulled a lot of stuff out of me," Zach says. When they are together, the pair put fun first. They play games of gin or Bananagrams, tease each other good-naturedly. "More her making fun of me. We rarely have a bad day."

The couple did marriage counseling before they wed, approaching their partnership like they do their sport -- giving it their all, in all ways.

"Zach knows me better than anyone else in the world," Julie says. "He's that person I'm vulnerable with. We grew up together. In the soccer world, it's really hard to root yourself."

For Julie, Zach is home. And that home is sacred. The couple decided long ago that their marriage would come first, before football, before soccer, before the World Cup and the Super Bowl and the raining down of international acclaim.

"Our relationship wasn't built on Julie's ability to play soccer and my ability to play football," Zach explains.

"Don't get me wrong," Julie clarifies. "We want to give sports everything we have. But this career isn't something you can do forever."

"Having a horrible loss in the Olympics was an awakening for me. It was a really long time before I felt normal again," Ertz says. Mary Ellen Matthews for ESPN

IT IS LATE afternoon, and Alyssa Naeher is driving Julie to their midtown Chicago gym for their second workout of the day. Naeher's side mirror is knocked off, so she wrenches her head hard left.

"You look like me on the field," Ertz jokes, dramatically swiveling her body, thick ponytail snapping. The women laugh, talk about Mike Trout's record-breaking contract for $36.8 million a year.

"Where's our multimillion-dollar payday?" Naeher asks.

"Right?" Ertz chimes in, noting that she and Trout are nearly the same age. (Ertz says she has no comment on the current USWNT lawsuit seeking equitable pay and treatment, preferring to "keep a one-track mind toward France.")

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Ertz reminds Naeher that she knows Trout personally, that he's a great guy. She and Zach have couples dinners with him and his wife. She says her second wedding anniversary is coming up, and she and Zach are going to buy each other surprise outfits to wear to dinner. She's worried about what Zach will pick. She usually dresses him.

"Hips Don't Lie" comes on the radio, and Ertz breaks into song. She makes an inspirational playlist every December, adding songs "over the year whenever I hear one that speaks to me in the moment." The last tune she added was "Sunshine," by Maoli, a breezy island bop celebrating true love. She says it reminds her of a trip to Turks and Caicos with Zach.

Earlier in the week, Ertz was interrupted by a soccer dad during dinner out. He said his 13-year-old daughter was holding herself back on the field and that he'd advised her to act like Ertz, told her, "It's OK to be a savage on the field. I guarantee Julie would destroy someone."

Ertz nodded along, pleased.

"My teammates all know not to go into a tackle when I go for it," she told the man.

Ertz is not ashamed of her rep for aggression. Or how observers interpret her game. "No matter what we do, somebody will have something to say about it." She shrugs. "That's just how it is if you're a woman athlete."

Ertz knows all too well the cruel vagaries of pro sports, especially for women, where scarcity of opportunity casts every high and low in crushing relief.

During the 2016 Olympics in Rio, Ertz was hitting her stride at center back. "The game against New Zealand was one of the best games I've played." Later came Sweden: the first time Team USA didn't win gold in 16 years and the first defeat for Ertz.

"I'd never lost with the team when I was on the field until that game," she says. "It didn't feel real."

After the loss, Ertz was the one U.S. player randomly pulled for drug testing. She was driven to the doctor with a member of the Swedish team. They both waited for hours to pee in a cup, Ertz biting her cheeks in silence as her opponent gleefully celebrated into her cellphone, the scene something out of a goofy European farce.

"I didn't get to see my teammates, give them hugs," Ertz says. "I didn't hear what the coaches had to say."

When she made it back home to Philadelphia, Zach was already with the Eagles in OTAs, and Julie found herself alone in an empty house. Zach flew in her parents to nudge her out of her funk. "And I didn't talk to them," she says. "I literally sat in silence for two weeks."

On her phone, she kept a photo of her near-miss block in the fatal game as her screen saver. "It was not a great time in my life," Ertz says, sighing.

When you are a defender, your job is basically proving a negative, your triumphs largely invisible while your mistakes scream loud as sirens.

"You could play a great game for 89 minutes, and then if you don't do one thing ..." Ertz quiets, shakes her head. "A forward can suck for 90 minutes, but if you score in overtime, no one remembers the rest of the game."

Ertz was benched from the national team after the Olympics. For nearly a year she didn't start, an abrupt and gutting life change.

"It was a really hard time for me. I never asked why. Probably never will. I don't want to know."

Ertz is not one for self-pity. She can do the USWNT math. The bench is deep with exceptional players. Rejection is in the DNA of the cutthroat selection process. Still, it was hard to reconcile.

"It's weird to talk about," she says. "I was pissed: 'I'll show you the mistake you're making by not using me.' I said that every day at practice in my head. Then as it went on and I wasn't playing, I started thinking, 'Maybe your life is going in a different direction than you think.'"

She considered retirement. Sitting out game days was almost too painful to bear. But "I realized my career has been started in those moments. I could either choose to sit there and be mad or be prepared and prove my point. I still had that pride."

"When you're dealing with adversity as an athlete, you can pout and point the finger at someone else, or you can reflect and ask yourself, 'How can I get better?'" Zach says. "That's what she did. She ramped up to another level."

For Ertz, aggression is a calling card. Jerome Miron-USA TODAY Sports

Ertz leaned in to the inescapable grind of professional sport. The monotony behind moments of elation, trudging through muddy parking lots to dimly lit practice fields to do the same drills she'd done almost every day for 20 years. She also doubled down on overall fitness.

"To be elite, my fitness had to go way up. And I had to accept that mentally it's going to be very, very hard and push past it."

Playing in the NWSL was a balm.

"Feeling wanted, at least somewhere," Ertz says, allowed her "to figure out where I belonged."

As it turns out, it was in the midfield. Asked by Ellis to sub as a midfielder for the Brazil game in the 2017 Tournament of Nations, Ertz didn't hesitate. She did what she has always done. She said yes and worried about the details later.

"I was told, 'Don't expect to be a midfielder.' And I kind of just stayed there. I was working my ass off. I was thinking, 'If this is the way that it's going to go, at least I'm going to leave knowing that I did everything that I could.'"

Observes Dames, "A lot of people would not mentally be able to overcome those obstacles. Her ability to reinvent herself in the midfield and become arguably the most vital piece of the U.S. team's success, it's special."

"This is not a normal thing what we do," adds Naeher. "It's hard to understand the psychological side of it unless you're in it."

Ertz still wants her passing completion to be higher. She wants more goals outside of the 18 she has. She wants to be fit enough to play seven games "at my top, because that's what it's going to take to win the World Cup." But she is #grateful for her hardships.

In the best case, failure begets knowledge, and Ertz has learned plenty. About her fortitude. About the limited value of what others believe are your limits. About going to the mattresses. She knows who she is now.

"Days after the World Cup, I couldn't wait until we could win the Olympics. And then days after we lost the Olympics, I couldn't wait for another World Cup. I thought, 'If I just won this, it would be everything.' And then you get there and you always want something else."

Ertz sensed there had to be more than leapfrogging from medal to medal, goal to goal. "All I had was soccer. That was my identity. If soccer didn't go well, nothing else was great." So she shifted her perspective. Less end game, more journey. Ertz started asking herself, "What else is there?" And her answer was faith, family and deep friendship.

"Everyone feels alone in this world," she says. "I felt alone in college, and I lived in a room with five girls."

Ertz pauses, takes a beat to ponder her spiritual growth.

"Sometimes it's hard. I want to be a really good role model, but at the same time, look, I'm still trying to grow up."

ERTZ LIVES OUT of a single suitcase. On the left side are her undergarments. On the right side, her toiletries. She packs only four outfits, two big old coats, leggings, sweatpants, tank tops. She's an expert at simplifying in the service of excellence, at winnowing life to the crux of what matters.

In third grade, Ertz's teacher asked the class to draw a dream board of what the children wanted their futures to be when they grew up. Her classmates drew pictures of houses and dogs and firemen and doctors and flowers and princesses. Young Julie drew a soccer player. It was the only image on her board.

Over coffee at a hipster café in the West Loop, Ertz contemplates her résumé: "I played soccer and I baby-sat. It would literally be that."

Ertz has already begun considering the end of her game. She is at her peak. And peaks do not last. That reckoning has not gone down easy. She does the mental prep, tries to focus on the joy that still awaits -- children, her foundation, paying it forward, her faith. But the verdict remains heavy.

"If I retire when I'm 55 or 28, it will never be the right moment. There is nothing that makes me as excited and joyful as soccer does."

Dames recently repositioned Ertz into the Red Stars' back line, even though she's ramping up for the World Cup at midfield.

"The soccer IQ needed for juggling those two positions at this level is huge," Naeher says.

"It wasn't best for her," Dames acknowledges. "But she said, 'Let's do it!' No hesitation. Not, 'Well, I need to get into the six and my spot might be in jeopardy.' Just a very simple, 'Yep, I agree. It's best for the team.'"

To compensate for the demands of dual positions, Ertz adds extra running to her workout, concentrates on specialized ballhandling. She rarely takes a day off; she is still, as her parents imparted decades ago, accountable. The exigent complexity drives her.

"When I'm called upon, I'm going to be ready."

After Red Stars practice, as her teammates trot off to showers and lunches, Ertz remains on the field. She does drills, gets in extra touches, examines her weaknesses, systematically dismantles them.

In the far corner of the field, she launches the ball repeatedly into a wooden kickboard, maneuvering and adjusting her footwork centimeter by centimeter.

Boom. Thump. Boom. Thump. Again and again she kicks.

It sounds like a heartbeat.