Until the 86th minute of the U.S. national team’s World Cup opener Monday, until his 6-foot-4 frame dwarfed a Ghanaian defender and he snapped a header into the net, until his is-this-for-real expression flashed around the globe, John Brooks was barely known outside the narrowest American soccer circles.

The 21-year-old German American center back did not make his U.S. debut until last August. Before entering at the start of the second half against Ghana for injured Matt Besler, Brooks had earned mixed reviews in four friendlies and played just 45 minutes in the three tournament tuneups.

If a hero were to emerge at Arena das Dunas in Natal, John Anthony Brooks was probably not going to be it. Clint Dempsey or Michael Bradley, maybe Aron Johannsson or Graham Zusi. Surely not Brooks.

But there he was, eight yards from the target as Zusi’s corner kick hurled toward him: head to ball, downward trajectory, one bounce . . . bliss.

“I just ran in the box,” he said, “and hoped the ball landed on my head.”

With the 2-1 victory, the United States landed in second place in Group G — level with Germany on three points but trailing on goal difference — leading to Sunday’s match against Portugal (no points) in Manaus. Two of the group’s four teams will advance to the knockout stage.

If, as Coach Jurgen Klinsmann indicated Tuesday, Besler’s hamstring ailment was a minor setback, Brooks would probably return to reserve duty this weekend. He would do so, though, with a much higher profile than he carried into training camp at Stanford University last month and to Brazil as a surprise choice for Klinsmann’s 23-man final roster.

Brooks beat out veteran Clarence Goodson for a ticket to Brazil, but with fellow center backs Besler, Geoff Cameron and Omar Gonzalez offering more experience at both the club and international level, he figured to remain rooted to the bench for most, if not all, of the tournament.

Besler’s injury, however, prompted Klinsmann to summon the Hertha Berlin player. As the coach later explained, Brooks, like Besler, plays on the left side of the central formation, while Gonzalez provides cover for Cameron on the right.

Brooks’s inexperience in pressure situations never concerned Klinsmann.

“It’s normal that when young players come through and have their first big opportunities that everyone is curious to see how far those players are already,” Klinsmann said. “We could see in every training session and we could see with his club as well that he’s a very good talent coming through the ranks. It was no problem for me at all.”

Brooks is among five rostered players with deeper ties to Germany than the United States — sons of U.S. servicemen and German mothers. All but midfielder Julian Green, 19, were born in Germany. All rose through youth systems in Germany.

In honor of his father’s home town (Chicago) and his own home town (Berlin), Brooks sports tattoos of Illinois and the German capital on his elbows.

With dual nationality, he served with both the U.S. and German under-20 squads and the American under-23 team before committing to the U.S. program last summer.

“It was not a hard decision; the U.S. really wanted me,” he said. The reality was the United States offered a greater opportunity to play internationally than Germany, a three-time world champion stocked with elite players.

The oddity of Brooks’s situation is that, had he not appeared in any World Cup matches, he would have remained eligible to represent Germany in the future. By entering Monday’s game (an official FIFA competition), he became “cap-tied” to the United States for the rest of his playing career.

Klinsmann’s German heritage and the other German American players have helped ease the transition. “They make it as easy as possible,” said Brooks, who has never lived in the United States.

Brooks speaks English well but at times struggles to find the right words.

Answering a question about entering the Ghana game, he said: “The first few moments I was very nervous but then I think I had my first, how do you say it? I don’t know it in English. Sorry, next please.”

Since his U.S. debut last year, Brooks seemed to fluctuate on Klinsmann’s depth chart. He started in a friendly at Austria last fall but fell out of favor with Hertha Coach Jos Luhukay, who publicly questioned his maturity.

In the spring, he did not show well in a 90-minute U.S. effort against Ukraine and was benched by Luhukay after getting a large-scale tattoo on his back. (The club said he was at risk of inflammation.)

“They expected more from him,” Klinsmann said of Brooks’s time in Hertha’s doghouse. “There he got a little bit of a lesson from his coach. It's part of growing.”

After playing inconsistently in the Bundesliga, Brooks said he did not expect an invitation to the 30-man U.S. training camp. He performed well enough to make the final cut, although many observers concluded, incorrectly, that Klinsmann chose him for grooming purposes ahead of future international competitions.

Brooks caught World Cup fever for the first time in 2006, when Germany hosted the tournament. Although he didn’t attend any matches in Berlin, “it hit me right in the face,” he said. “It was a good feeling to experience it.”

Germany’s coach at the time? Klinsmann.

Brooks, Klinsmann and the others with German connections will face an emotional test in the June 26 group finale, a meeting with Germany in Recife.

Brooks left no doubt about his playing allegiance.

“When I am here, I am full American,” he said. “I play with heart for America.”