On the surface, 180 minutes of friendly soccer yielded plenty of positivity around the U.S. men's national team this week. Two tests against World Cup participants yielded three goals scored and none conceded. An ultra-young USMNT kept two clean sheets using two different goalkeepers behind two different pressing schemes. It created chances in two different attacking shapes against Morocco and Uruguay, two of the sturdiest defensive platoons on their respective continents.

It claimed two results that would likely be sufficient to see it through a World Cup group, and that alone will fuel optimism for months to come.

Those results, though, were a bit deceiving.

Beneath the surface, there were flaws.

Gregg Berhalter, the team's head coach, knows this, and hinted at it after a 3-0 win over Morocco and a 0-0 draw with Uruguay. He spoke about vulnerability on Wednesday, and danced around some questions without doling out his customary praise on Sunday. He likely knows that his team's Expected Goal differential across those 180 minutes was, according to most models, negative. He knows that, amid all the promise that his players wield, they are an incomplete unit that hasn't yet learned to paper over its cracks, which were evident as World Cup prep kicked into gear.

There are, of course, also reasons for optimism. The bubbliest of the many is a 19-year-old who's been stuck in a suboptimal position at his club, but whose potential the USMNT is beginning to unlock.

The worry, however, is that deficiencies at both ends of the field could mask promise in Qatar come November.

Sunday's tussle with Uruguay offered no solutions to the USMNT's two most nagging dilemmas. Neither of its strikers, Jesus Ferreira nor Haji Wright, looked capable of leading a line under Uruguayan pressure. Both of its left-sided center backs, Aaron Long and Erik Palmer-Brown, looked shaky.

They weren't punished by Uruguay's B-plus team, but that doesn't mean they won't be in five-and-a-half months.

The search for a second center back goes on

When Miles Robinson crumpled to Atlanta United's turf last month, and when subsequent scans revealed a torn Achilles, a seemingly settled partnership at the heart of the U.S. defense ruptured. Walker Zimmerman, as he embraced an off-field leadership role, had established himself as one starting center back. Robinson was "so valuable" next to him, Berhalter said last month, because pressing teams "need guys that can win duels convincingly" and that possess elite speed to clean up messes behind a high back line.

Robinson could do both of those things.

Long tried to on Wednesday, but got rolled and spun by Moroccan striker Ayoub El Kaabi. And the same unawareness that triggered problems on Wednesday emerged again on Sunday. In the fifth minute, a split-second of indecisiveness dragged Zimmerman with him toward the ball, and left Darwin Nuñez free at the far post.

In the 23rd minute, Long dawdled in no-man's land in the penalty area, and failed to spot Manuel Ugarte lurking free at the top of the box.

Long, though, seems to be the primary candidate to partner Zimmerman in Qatar, especially after Palmer-Brown's shoddy second half. The 25-year-old was primarily, and sometimes singlehandedly responsible for a few of Uruguay's best chances. A simple, straight ball over the top caught him flat-footed in the 94th minute, and nearly won the game for the visitors.

Cameron Carter-Vickers looked solid in 45 minutes on Wednesday, but he's never started a game under Berhalter. Chris Richards has the most raw talent of the lot, but he's 22 years old and currently injured. They're the two most intriguing options, but the U.S. will enter September, its last window for World Cup tuneups, with those two having never faced a World Cup-caliber opponent alongside Zimmerman.

Whoever does emerge will inevitably shoulder responsibility. This U.S. team is at its best when pressing ravenously. As Berhalter said, pressing puts stress on center backs — stress that Long didn't handle all that well on Wednesday.

Scoreboards didn't reflect any of that, but more predictive metrics did. The USMNT's 3.7 Expected Goals Against over the two friendlies, per Tru Media's Paul Carr, suggest the defensive cleanliness was misleading. Backup fullbacks exacerbated issues, but Sergiño Dest won't solve them, and they could limit Berhalter's aggressiveness in Qatar.

A no good, very bad day for USMNT strikers

The USMNT's single biggest positional weakness, though, is at the top of the field, where encouraging Wednesday performances gave way to Sunday flops.

Ferreira's lowlight was a wayward header on the Uruguayan doorstep. The real problem, though, was nearly everything else. Ferreira can influence games without scoring, but on Sunday, most of his impact was negative. He seemed to struggle in tight spaces with European title winners breathing down his neck. His first touch was uncharacteristically sloppy.

And that, precisely, was always the concern with Ferreira — that characteristics developed in MLS, against weaker competition, would crumble against unfamiliar resistance.

Sixty minutes, of course, is far too small a sample size to draw grand conclusions. And conclusions could have been wildly different if a well-struck 19th-minute shot had found a corner, or if DeAndre Yedlin's cross had been a half-foot lower or a half-ounce more controlled. Berhalter knows not to overreact to one game. He has said that club form will be his primary evaluation tool — and at FC Dallas, Ferreira has sizzled.

But he didn't offer the USMNT a target or outlet on Sunday. He didn't score or create.

Wright, who was crisp on Wednesday, then entered at the hour mark, and completed one pass in 30 minutes.

He could've counted his touches on one hand.

He was all but invisible.

The U.S. doesn't necessarily need goals from its striker, but it needs something, much more than it got on Sunday.

The brilliance and intrigue of Yunus Musah

The optimistic spin on Sunday's performance, on the other hand, is that ball progression and chance creation are far more sustainable than finishing; and that the USMNT has found a ball-progression wizard.

His name is Yunus Musah, and he is an absolute delight to watch. He skates by opposing midfielders and zooms from defensive third to attacking third with the ball on a string. He has qualities without precedent in American soccer, and again, he is only 19.

To empower him, Berhalter has tweaked the USMNT's shape in possession this month. Musah has dropped deeper, next to Tyler Adams in a 3-2-5/3-2-2-3 (against Morocco) or a 4-2-4 (against Uruguay), when the U.S. builds from the back. He now regularly picks up the ball from center backs, and can foil an opponent's press with one simple drop of his shoulder and burst of acceleration.

"When you play the 3-2-2-3 type of shape, you have a guy deep that can take people on the dribble and break lines dribbling, it's really valuable," Berhalter explained Wednesday.

On Sunday, he raved: "Yunus is a guy that just blows me away, at his age, what he can do. Craaazy level of talent."

The next step, Berhalter said, is the end product, the final or penultimate pass. It's the ability to carry the ball the length of midfield and then release it to teammates who can do damage with it.

That "finishing attacks phase," in general, is where the team struggled on Sunday, Berhalter said.

But it largely withstood Uruguay's pressure. It will never perfect any phase of play, but it's moving toward mastery of the middle third of the field. That's where the raw ability of players like Musah, Adams, Weston McKennie and Christian Pulisic takes over. Their ability is why this USMNT is so tactically flexible, and potentially dangerous in Qatar.

It's those flaws, though, that can unjustly dump a talented team out of a World Cup. And they'll loom over this youthful, innocent American team until they're solved.