CHICAGO — How far the U.S. men's national team goes at the World Cup will depend on its back line.

And right now, that's something of a scary prospect.

The USMNT fell to Germany 2-1 in its final game before its World Cup campaign starts Friday against Paraguay. No shame in that. The Germans are four-time World Cup champions and currently ranked 10th in the world.

The USMNT also showed moments of being truly impressive, starting with their response to conceding a goal just two minutes into the game. Antonee Robinson equalized on a banger in the 37th minute, and the Americans kept fighting until the final whistle. Literally and figuratively.

And the final send-off game has little bearing on what the USMNT does once the World Cup begins.

The USMNT won or drew in the last game before the 2006, 2010, 2014 and 2022 World Cups, and didn't get further than the round of 16 in any of those tournaments. The last send-off game they lost was in 2002, and they responded with a run to the quarterfinals, their best finish since 1930.

But the back line continues to be an issue.

The USMNT has given up 11 goals in four games this year. They haven't recorded a clean sheet since a 2-0 win over Japan in September, a span of eight games. Goalkeeper, long the strength of the USMNT, remains an uncertainty, if not a weakness, with neither Matt Freese nor Matt Turner giving the security-blanket vibes of a Tim Howard, Kasey Keller or Tony Meola.

The status of Chris Richards, who along with Tim Ream had locked down starting center back spots, is still in doubt after he tore two ligaments in his ankle at the end of the Premier League season. Richards was unavailable for the Germany game, though he was able to train with the USMNT the day before.

"Obviously he's a big-time player," Ream said after the Germany game. "It'll be good to have him back. He's a big voice, he's a big personality, commanding center back and someone who's been relied on heavily over the past 18 months. So it'll be nice to hopefully have him back.

"Then, like I said, we see what combinations get picked and we go from there. But it'll be nice to get him back in full and raring to go for the group stage."

If Richards can't go, though, or he has a setback, it could leave the USMNT vulnerable. You saw it against the Germans.

Granted, Kai Havertz is a menace and he's going to make life tough for pretty much every opponent. But leaving him open, or open enough to get his head on the ball and catch Freese flat-flooted can't happen. It doesn't matter if there were shenanigans in the scrum that the referee should have caught. The USMNT can't afford such a glaring breakdown in coverage.

Same for Germany's second goal. Havertz made a nifty pass to Leroy Sané, who found an alley between Ream and Miles Robinson. Freese tried to make a diving save, but the ball was just beyond his outstretched hands.

"There was times where you can see the eagerness in the team to go and press and try and win the ball back and, at times, we were a little bit disjointed in how we pressed," Antonee Robinson said. "That's what good teams like Germany want you to do. They want someone to jump and someone not to follow behind so that they can play around it.

"I think when we got a bit more comfortable knowing when to press and when to just sit on the block, we were a lot better."

The good news for the USMNT is it won't face a team of Germany's caliber for at least three weeks. (Apologies to Paraguay, Australia and Turkey, but let's be real.) A team can grow into itself over the group stage, establishing chemistry and plugging holes.

Just look at what Argentina did four years ago. It lost to Saudi Arabia in the opener, for heaven's sake, and went into its final group-stage game needing a win to ensure it advanced. Three weeks later, Lionel Messi and the Albiceleste were World Cup champions.

"Disappointed that we lost, but many positives to take," Robinson said. "I feel like conceding that early, we could have easily crumbled and it could have been a very, very bad day to be going into the tournament with. But we fought back and at times played some really good football and looked good, looked competitive."

"These tests, that's what that's for," Robinson added. "We've still got time to shore up a few mistakes that we've made."

They're going to have to. Their World Cup run depends on it.

Follow USA TODAY Sports columnist Nancy Armour on social media @nrarmour.

This article originally appeared on USA TODAY: USMNT back line remains a concern going into World Cup