WASHINGTON, D.C.—Momentum is a funny thing in sports. In an era where the performers emphasize taking everything one game, one half, or even quarter at a time, the idea of creating a run of good form and having it carry over is taken as gospel.

Never mind that no one ever knows when a bad streak will suddenly end or a string of positive results will abruptly lead to a series of disappointing performances.  

And so it goes with the U.S. men's national team, which hopes yesterday’s come-from-behind win over a good Peru team will give it some momentum it can take into October's clash with Mexico with a trip to the 2017 Confederations Cup on the line.

The Yanks know just how fickle Big Mo, as famed American football coach Bum Phillips once coined it, can be. They came into this summer’s CONCACAF Gold Cup on a roll, unbeaten in five straight games, including a thorough victory over Mexico and road wins over the Netherlands and Germany.

With those results in its back pocket, the team proceeded to play a brand of tepid soccer that caught up to them when Jamaica upset the U.S. in the semifinals. In this instance, momentum did them no good and it ended without notice.

Still, confidence is contagious and the Americans are hoping the Peru win will see it go viral.

“It was just one game, yes, but it gives you confidence and we can take that to (the) Mexico” game, said defender John Brooks.

Added goalkeeper Brad Guzan: “Winning is a good habit to get into so it’s important we started to do that again.”

For some, it was less about creating positive momentum and more about ending the bad form from the summer.

“It was good to get the win," Jozy Altidore said. "Coming off a tough Gold Cup—disappointing for a lot of us—it wasn’t perfect by any means, but it does a lot for your morale when you win a game."

And beating a team that just came in third in the Copa America this summer certainly helps.

“For the whole team it was important and good that, after that Gold Cup, that we show we can beat a team that played a good Copa America and always plays good in South America," said midfielder Jermaine Jones, who returned to the team after missing the Gold Cup because of injury.

BATTLE ROYALE IN DEFENSE

Inconsistency in the backline, especially at center back, played a major role in the United States' poor showing in the Gold Cup, where few of the defenders besides Fabian Johnson stood out.

The roster for this camp, which continues in Boston ahead of Tuesday’s friendly with Brazil, is top-heavy with central defenders. eight in total. This fact was not lost on any of them.

After not being included in the Gold Cup roster, Geoff Cameron, Matt Besler, and even Jonathan Spector, who hasn’t been capped since 2012, were brought back for this camp. The message was clear: the backs need to step it up.

For the most part Klinsmann was pleased: “I think they got the message,” he said.

“You see the roster and that gets your attention,” said Tim Ream, who plays centrally for Fulham but had a solid showing yesterday as the left fullback. “But competition is good and pushes us to play better. We had a really good week of training and I think you saw that tonight.”

Against Peru Klinsmann used every central defender except Spector, who didn’t arrive in camp until mid-week. Brooks began the night paired with Omar Gonzalez, who was replaced at halftime by Ventura Alvarado. Brooks gave way to Besler midway through the second half.

Meanwhile, Ream and Michael Orozco both slotted out to right and left back, respectively, and Cameron replaced Orozco after the break.

“A lot of guys going for a few spots,” said Besler, when asked about the number of center backs in camp.  

With that much competition and experience in camp, a poor showing can—and quite frankly, should—lead to benching, at least until after the Mexico match. That’s not good news for Gonzalez, who made a mental gaffe on Peru’s goal. Rather than close down on Daniel Chavez, Gonzalez retreated and Chavez’s shot ended up in the back of the net.  

The usually affable Gonzalez did not speak to reporters after the game, leaving for the team bus while Klinsmann was conducting his post-match press conference.

Ream was the only defender who went 90 minutes and drew Klinsmann’s praise for his performance.

“Tim Ream very had a very solid game,” Klinsmann said. “Won a lot of one-v-one and played simple.”

Ream played a lot of fullback during his past two seasons at Bolton but said it’s a different animal at the international level: “The way the guys run at you is the biggest adjustment," the St. Louis native said. "A lot of speed, a lot of skill.”

Still, there’s no guarantee that a good display in September will result in a start against Mexico next month.

Klinsmann said mid-week that veteran DaMarcus Beasley, who started at left back in last year’s World Cup but wasn’t included in this camp, would be part of the lineup against Mexico. The versatile Johnson, who started most of the Gold Cup games for the U.S. at left back, also missed the camp as he recovers from an injury that sidelined him in Germany. Klinsmann is optimistic he’ll be available next month. 

NO DOUBTS IN GOAL

One area where there are few questions for the U.S. is goalkeeping. Even with Tim Howard, the most-capped goalkeeper in U.S. history, returning to the fold after a 14-month national team hiatus, Klinsmann left no doubt that Brad Guzan is his man—at least through the Mexico game.

Guzan solidified that position with a strong outing against Peru. There was little he could do on Chavez’ strike after it took a weird deflection but in the 66th minute he made a series of saves on bang-bang shots that ended with him sprawled on the RFK turf, ball in hand, as Peruvian players tried to pry it loose.

“It came from a wide free kick and I saw it kind of late as it came over our first defender,” Guzan explained. “I was happy to keep the first one out and then I was able to keep the second one out. It kind of stuck in my leg and at that point you’re doing all you can to keep the ball out of the net. I was happy to keep it from going behind me.”

The play was pivotal as a minute later the U.S. scored the game-winning goal.

After spending the first eight years of his career as a backup relegated to an occasional cap, Guzan has now started 10 straight games for the U.S. His 38 caps is now fifth all-time among American goalkeepers, behind only the Mt. Rushmore of U.S. keepers: Howard (104 caps), Kasey Keller (102), Tony Meola (100), and Brad Friedel (82).

ALTIDORE PLAYS BIG

When you score both of your teams goals in a win, it’s easy to focus on the goal-scoring. And while Jozy Altidore deserves credit for his brace against Peru, it was the dirty work as a target forward—playing with his back to the goal, holding up the ball and finding teammates—that drew his coach’s and teammate’s praise.

"He's a guy that sometimes it looks like he's lazy and sometimes he's maybe not fit. But I know him a little bit now and know that he's going to try to look forward and try to help the team and try the best,” said Jones. “He does a lot of things, small things, to help the team and when he does them it gets the other players into the game and we are all playing off that and making the runs and creating chances.

"He was very strong out there tonight. And of course he scored two goals which is big. I’m very happy for him.”

Added midfielder Alejandro Bedoya: "Jozy is a guy that has experience now. He's been through a lot, and I think he's handled it really well. Even in the league, when he wasn't starting for whatever reason, he was coming off the bench and still being a spark and working his butt off for the team."

Altidore suffered a hamstring injury in May and rushed back to make the Gold Cup roster but was obviously not 100 percent and was dropped after the group stage.

"I feel like I'm getting there," Altidore said. "Your body might feel good but your mind isn't there yet. A lot of people don't understand how it is with that kind of injury because they don't go through it."

Altidore is optimistic his return to health, and form, will allow him to be part of the game with Mexico next month.

“I gotta get there first,” he said. "Hopefully, it’ll be nice. I haven’t gotten a chance to play a lot of big games against Mexico unfortunately, for whatever reason. So hopefully I can get out there if I’m fit and the manager picks me. Hopefully I can be the difference."

Brooke Tunstall is an American Soccer Now contributing editor and ASN 100 panelist. Follow him on Twitter.