Success in soccer is a fragile thing.

The United States entered Friday night’s showdown World Cup qualifier against Costa Rica unbeaten in fourteen straight games under Bruce Arena, one more big win away from all but locking up its trip to Russia next summer.

It felt like a sure thing.

And then – an uneven opening half hour, a pro-Costa Rica crowd in New Jersey, an opening goal from Marco Ureña, and all the confidence culled from the last seven months went up in smoke.

The U.S. never recovered on Friday night. Costa Rica put them away 2-0. And just like that, this qualification campaign – which was plunged into crisis in Costa Rica last November – is right back on the brink.

When Arena took this job for the second time last November, he knew that the margin for error was thin. Now he’ll find out just how thin.

SEE MORE: Player ratings for USA’s performance against Costa Rica

For the first time since Arena retook the reigns, the U.S. is legitimate adversity. Lose in San Pedro Sula on Tuesday, and the U.S. will be on the outside looking in for an automatic qualifying berth.

Mexico is in. Costa Rica will likely join them on Tuesday. It’s down to the U.S., Honduras, and Panama to scrap for the region’s final spot and a half, with the fourth place finisher bound for a playoff with a correspondingly placed finisher in Asia.

Needless to say, it’s not where the United States thought they’d be when this Hexagonal opened nine months ago. The U.S. had, after all, won the Hex in 2005, 2009, and 2013.

Now, with this defeat, headed for their worst Hex finish since 2002 or ever, the U.S. has done something it hadn’t done previously since 1957: Lose two home qualifiers in a single cycle.

The Americans took one on the chin at Red Bull Arena. Arena said his team was both “outplayed and outcoached,” and he wasn’t wrong.

Costa Rica came ready to play. They overran the U.S. in central midfield, swarmed Christian Pulisic, and, in the big moments in both boxes, got the plays they needed to win.

Was the U.S. overconfident? There’s plenty – including the decision to hold the game in the New York City area – to suggest that it was.

Neither Arena nor Sunil Gulati, of course, could have predicted that Geoff Cameron would choose this night to have his worst U.S. game in years, or that Ureña would spend the night finishing like Paulo Wanchope.

But this is a wakeup call. The U.S. hasn’t tasted a shred of adversity since the coaching change, and its success this year created a false sense of security.

CONCACAF qualifying might be forgiving – as evidenced by the fact that the U.S. still controls its own destiny to get to the World Cup – but those back-to-back losses to meant that the team was never likely to sail into Russia unabated.

It’s now that the Arena era starts in earnest. The honeymoon is over.

Now, over the next three days, the best manager the U.S. has ever produced will have to pick his team up off the mat and get them ready for the national team’s most important road qualifier in recent memory.

Playing in Honduras is hard enough under any circumstances. But in these circumstances? With a newly-weakened U.S. team standing as the only obstacle between Los Catrachos and a straight line to the finals?

It’s going to be crazy in San Pedro Sula on Tuesday. An absolute cauldron.

How will this team respond? The last time the U.S. lost a home qualifier, of course, they followed it up by getting walloped on the road in the game that cost Klinsmann his job.

We’ve heard plenty said this summer from the likes of Tim Howard and Michael Bradley about how the team’s mentality, thanks in large part to Arena, is much improved since that 4-0 drubbing last November – how players understand their roles and are playing for each other.

Easy enough to say when you’re winning. But it’s in difficult times that the character of teams is tested, and for the U.S., that test is now looming.

They should embrace the challenge. Friday night’s effort was an embarrassment. The U.S. wasn’t just outplayed. It was also out-competed. Pushed around. Costa Rica took the game to the U.S., and in this region, no matter the competition and no matter the location, that’s a recipe for disaster.

Tactically, Arena will make the adjustments. Darlington Nagbe won’t be deployed as a central midfielder in a 4-4-2. Tim Ream and Fabian Johnson will be gone, in favor of the Beasleys and the Dempseys who know CONCACAF inside and out.

Then it will be up to the players to get after it. All teams have bad nights. The U.S. certainly had one against Costa Rica. But if this U.S. team is good as we think it as, as good as it’s said it is, it’ll bounce back next time out.

If it doesn’t, it might not deserve a World Cup berth in the first place.