Building an Olympic team is tricky business. Because you’re constructing a team more or less from scratch, and focusing all efforts into a very limited number of meaningful games.

By the time any major flaws have been identified, it might be too late. Because flaws proving more significant than originally believed can turn fatal, and right quick.

There’s no sugar-coating it: the United States is in a dark corner after Saturday’s surprising 2-0 loss to Canada. Caleb Porter’s team must win Monday against El Salvador to ensure passage into the critical semifinals in Kansas City.

A draw against El Salvador, a tiny nation now inspired by the massive Olympic opportunity in front of them, probably won’t be enough for the U.S. under-23s.

So, about those “flaws:”

Dynamic formations and shrewd, fluid arrangements of so much attacking talent doesn’t mean a thing, as we can see, if the old-fashioned elements of leadership and want-to come up missing. Or, perhaps, were never there in the first place. Without the benefit of meaningful matches to test these elements over the last few months well, you never really know until you know. You know?

Saturday, “urgency” went on holiday on the U.S. side. The Canadians ran and ran and poured everything they had into the night. Too many American players might be asking if they did the same Saturday.

Going into the match, you could say there was definitely still a little bolt-tightening to be done in the U.S. defense. Seeing things unravel so spectacularly against Canada, it looks now like more than that. The problems start with center back Ike Opara, who just never looks completely comfortable or very smooth back there. His timing and positioning aren’t as astute as central partner Perry Kitchen, but that’s not the least of it. Some nervous indecision near goal nearly turned disastrous as Opara almost sneaked one past Bill Hamid at the near post in the first half. He got all turned around on a Canadian break midway through the second half, and then completely lost his mark on Canada’s second goal.

Opara can definitely can be a bother on offensive set-plays. But that’s not enough, and that spot looks like a real doozey of a U.S. problem.

The first Canadian strike was clearly on goalkeeper Bill Hamid, whose inexperience became a crusher. He was way too timid in claiming what should have been a routine ball into his six-yard box. By failing to grab the floating corner kick at its highest possible point (Goalkeeping 101) and not attacking the moment with authority, he turned a fairly benign cross into a fiasco.

Freddy Adu isn’t playing badly, really, but he’s sure not anything to shout about, either. Bottom line: he’s not doing enough. The U.S. captain (and most experienced international man) must press the game more and ask further questions of defenders in front of him. He’s quite competent in helping the Americans keep possession in the middle third. But he’s not stretching defenders the way Brek Shea did on the left (for a half Saturday, anyway). And when Adu came into the middle after the break, he was even less effective, never establishing himself as the playmaker Porter apparently asked him to be in a halftime tactical adjustment.

Speaking of that tactical adjustment: it didn’t work. Not at all. Joe Corona, Thursday’s three-goal scorer, wasn’t finding the spaces that he did against Cuba’s awful defense. And, as noted, Adu wasn’t having his best night on the right wing. So Porter removed Corona, switched Shea to the right, redeployed Adu to attacking midfielder and added Joe Gyau to the left. Result: things got worse. Only in the last, desperate 10 minutes did the Americans begin seriously threatening Canadian goal. Down by two at that point, it was too late.