TORONTO — When it comes to scouting the opposition, John Herdman knows what he knows — and what he does not.

Herdman’s Canada national team will face Gregg Berhalter’s US national team on Tuesday at BMO Field in a crucial Concacaf Nations League match as the two vie for top spot in Group A of League A play (.

“They’re very hard to break down,” said Herdman on Wednesday. “No team has been able to, outside of Curacao, really cause the US any trouble in their build-up play. The Uruguayans struggled, the Mexicans have struggled and a lot of the goals have seem to come in transition and in the last 30 minutes of the game. That’s when they seem to concede.

“Defensively they’re one of the best in Concacaf. They fight for every ball, they’re able to cover ground quicker than most and they’ll do that for 90 minutes. So for us there’s an awareness of that: that you’re going to be pressed, they’re going to harry you, they’re going to be on every touch, so some of the principles training this week is around that.”

What is less clear is who will be suiting up for Berhalter’s side. Herdman will have keenly watched their 7-0 win over Cuba on Friday, but how much that side will resemble the one that squares off against Canada is anyone’s guess. Regulars from the US's Gold Cup run like Toronto FC captain Michael Bradley, D.C. United winger Paul Arriola, New York Red Bulls defender Aaron Long, Newcastle fullback DeAndre Yedlin and Columbus Crew SC forward Gyasi Zardes were all held out of Berhlater's starting XI Friday. Only Arriola played at all.

“We know who that front group is going to be, the front five. There is going to be some consistency about that,” Herdman said. “It’s that back-four that is constantly rotated, and that’s where you’re trying to target certain individuals. It’s difficult because you don’t know who is going to be there. A lot of players have rotated through that team.”

While Herdman remarked that Mexico hadn't figured out how to disrupt the US buildup, he expressed admiration for the challenges they caused the Americans' on the other end.

“The Mexicans have a very deliberate style and an intensity in how they just won’t let Berhalter’s machine settle into a rhythm," Herdman said. "That’s how I’ve seen [the US] develop. They’re like a well-oiled machine: everything works off a trigger, off a cue, and if you’re able to disrupt that rhythm then the team struggles.”

Canada will try to take a page out of the Mexican playbook.

“Mexico just unsettle them,” highlighted Herdman. “But Mexico are underpinned by this will that they will not let the USA beat them. That’s the difference: they will never let the USA beat them. That’s something that I’m sure the US will be saying about Canada, but I’m hoping our will to want to beat them, and what it will do for our country, will be a lot stronger.”

The players too are aware of that facet.

“They’re going through a change, trying to figure themselves out,” assessed Toronto midfielder Jonathan Osorio. “It’s a talented team; if they start clicking it will be a dangerous team.

“They know that they have a lot more to give, a lot more to show, than they have in the past few games. So that’s what they’re looking to do, looking to prove that they’re still the US and we’re still Canada. And us, the opposite. We’re trying to show that we can be talked about now in the same breath.”