ON FRIDAY NIGHT in Edmonton the U-20 United States women's national team won a close-fought 1-0 victory over Brazil in its second game of group play in the U-20 World Cup.

Needing at least a draw to stay alive after the team's opening loss to Germany, the U.S. battled back and forth with Brazil until finally finding the breakthrough in the 82nd minute on a goal by Lindsey Horan.

The U.S. will now head into its final match of group play against China on Tuesday (4 p.m. ET; ESPN2), and can advance to the knockout round with a win, or possibly a draw, depending on the result of the Germany-Brazil game in the other Group B match-up.

Here are three things we learned from the U.S.'s win.

Summer Green was tremendous

Although Lindsey Horan picked up the game-winning goal, the true difference-maker for the U.S. was University of North Carolina junior Summer Green. She entered the match in the 66th minute, coming on for fellow forward Makenzy Doniak, and right away Green provided the U.S. offense with a spark.

In her first minute on the field, Green found midfielder Rose Lavelle behind the Brazilian defense for an open chance and, within the next 10 minutes, Green managed to put together a nice combination with Horan in the box and get off two solid flank services.

Then, in the 82nd minute, it was Green's effort that helped the U.S. secure the decisive goal. Battling against two Brazilian defenders in the corner, Green won the ball, drove toward the endline, and found Horan on a beautiful layoff across the face of goal.

The play was typical of a UNC player, coming as much from effort as anything else, something the Tar Heel program under Anson Dorrance has prided itself on for four decades.

While Dorrance is sometimes criticized for favoring effort, fitness, and speed over possession or technical prowess, his players have been key contributors to the U.S. women's program for years. In fact, in the 2012 World Cup, Tar Heels Crystal Dunn and Kealia Ohai combined for the game-winning goal in the final.

The U.S. Was Tactically Naive

The U.S. U-20 squad, much like the senior women's squad at the moment, has been playing in a 4-3-3 setup.

However, the U.S. U-20 team is not taking advantage of the natural advantages of a 4-3-3. In such a system, the three frontrunners are generally expected to apply high pressure to an opponent's back line, while the three midfielders clog the center of the field and, hopefully, dominate possession there. Because the system has no natural width in the midfield, it counts on a team's outside backs to push forward whenever possible.

On Friday night, the U.S. forwards only intermittently pressured Brazil's back line, instead allowing the South Americans to carry the ball well up the field before closing them down. And, when the U.S. forwards did pressure, they often did so individually and not as a collective group, making it easy for the Brazilians to pass around them. The U.S. outside backs, just like in the opener against Germany earlier this week, rarely ventured forward, leaving the wide forwards without much support.

Finally, the U.S. refuses to play out of the back, hindering its ability to retain possession when goalkeeper Katelyn Rowland gets the ball. Instead, just as the U.S. did against Germany on Tuesday, Rowland simply smashed the ball far upfield with her punts. This often left the U.S. forwards in the position of trying to take down a 60-yard ball in traffic, or flick it on to teammates who were often 20 yards or more away from each other.

At the very least, the U.S. could use these long balls to stretch the field early in the match and then transition to a possession game. But so far the team has failed to do so, and has struggled to establish possession.

The U.S.'s attacking corner kicks also seem poorly worked out, as the two players on the goalkeeper are apparently being coached to vacate the six-yard box as the service is about to be played in. On Friday night, this left Brazilian goalkeeper Leticia to come out and easily grab a number of uncontested balls.

In total, the U.S. had seven corner kicks, none of which provided any serious danger to the Brazilian goal.

U.S. U-20 coach Michelle French, whose resume prior to being named the U-20 coach was mostly a series of short stints as an assistant, needs to do a better job of preparing the U.S. as it heads deeper into the tournament.

Sullivan Struggled; Purce Stepped Up

Midfielder Andy Sullivan, who has played the role of a holding midfielder for the U.S. in both of its games in the tournament, once again made a number of dangerous mistakes in possession on Friday night.

Sullivan's mistake against Germany on Tuesday led to the German's game-winning goal, and against Brazil she continued to struggle. Her poor touches and giveaways both in the U.S.'s defensive third and while the U.S. was in transition once again led to a number of dangerous counterattacks. Fortunately for the U.S., Brazil was not able to capitalize.

On the other hand, wide forward Margaret Purce improved her game considerably. While Purce struggled to make a different against Germany in the U.S.'s opening game, against Brazil, Purce was a bright spot in the U.S. attack.

Against Brazil, Purce repeatedly made driving runs down the wing, did well holding the ball up in transition and made a number of excellent plays defensively. She nearly got a goal, smashing her shot from outside the area against the crossbar in the 46th minute.

John D. Halloran is an American Soccer Now columnist. Follow him on Twitter.