The United States women’s national soccer team entered the 2019 World Cup as the favorites because of a loaded roster. Alex Morgan is the biggest name on the team. Tobin Heath, Lindsey Horan and Megan Rapinoe are also among the best players in the world.

Julie Ertz is on that list, as well. While some sports fans might know her for being the wife of Philadelphia Eagles’ tight end Zach Ertz, others know Julie Ertz as the most important piece to Team USA’s championship defense.

Ertz, known as Julie Johnston when she was unmarried and first competed in the World Cup, was a key figure on the 2015 U.S women’s national team. She played every minute of the tournament on the way to a World Cup title, doing so as the second-youngest member of the team at just 23 years old.

Four years later, a more experienced Ertz will shoulder even greater responsibility, playing a new position for a team that expects nothing less than another title. She was a center back on the 2015 USWNT but now occupies the role of a defensive midfielder.

Ertz is the rock of the USWNT. She’s given more responsibilities than just about anyone on the squad, and she’s certainly up for the challenge.

“When you look at the '6' position, it is such a critical position. Who can be that player that can cover ground and break up plays, who can win the ball in aerial battles and who also has the ability to connect with a pass? Well, we've seen that in JJ,” USWNT coach Jill Ellis told Sporting News. “Seeing her play there frequently with her club is certainly beneficial. We looked at different players in that spot, but ultimately it's just a really good fit for her.”

Julie Ertz USA Soccer Julie Ertz #8 of the United States passes the ball in the first half against Mexico at Red Bull Arena on May 26, 2019 in Harrison, New Jersey. Photo: Elsa/Getty Images

The four years since the USWNT won its record-setting third World Cup have been far from perfect for both Ertz and the team.

A year after winning the World Cup, the U.S. failed to even medal at the 2016 Rio Olympics. Ertz was then benched for almost a year, forced to watch from the sidelines as the team struggled in international competition.

Ertz found her way back into the USWNT starting lineup in 2017, moving to the position that she was playing for the Chicago Red Stars in the National Women’s Soccer League. As Ertz changed positions, so did the fortunes of the U.S., whose only loss in the last year and a half came early in 2019 against France.

“I was told, ‘Don't expect to be a midfielder.’ And I kind of just stayed there,” Ertz told ESPN.com. “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.’”

If anyone could go from the bench to the linchpin of the best team in the world, it would be Ertz.

The Arizona-native was named the 2014 NWSL Rookie of the Year a year after she was a First-Team All-American at Santa Clara. Ertz was named the 2017 U.S. Soccer Female Player of the Year, and she enters the World Cup with 18 goals and two assists in 81 appearances for the USWNT.

“It was a horrible heartbreak that I’d never had before,” Ertz said in regard to being ousted by Sweden in the Olympics, via the team’s official website. “It feels like we’re coming off a loss. This year, with the chance to beat Sweden, I definitely have a chip on my shoulder now. Last round, I had nothing to lose. This time, it feels like I have everything to lose.”

It’s championship or bust for Ertz and the USWNT, who make their 2019 World Cup debut against Thailand Tuesday afternoon.