It feels like the Portland Timbers’ second major challenge of the 2018 season, though in truth, it’s probably the team’s fourth. Sunday’s visit to Mercedes-Benz Stadium to face Atlanta United comes after a March loss at the New York Red Bulls, an April win over New York City FC, and a June draw with Sporting Kansas City. All three of those teams should be contenders five months from now, and amid that gauntlet, the Timbers have produced encouragingly mixed results.

But there is different feeling about Sunday’s game, though, just as there was a different feeling around that April meeting with New York City FC. There was something daunting about that NYCFC side that visited, then, just as there’s something grandiose about the challenge that lays before Portland this weekend. There’s an opportunity for accomplishment, here, that just didn’t feel there when the Timbers visited New Jersey or welcomed the West’s leaders.

“You can see that offensively, it’s a very strong team,” Portland head coach Giovanni Savarese said of Atlanta, in his weekly press conference. “It’s a team that has resources, creativity. They’re very dynamic. They can be dangerous and punish you even in moments that, maybe, they’re not playing as well, because they have the quality to score goals and create situations.”

That match against New York City felt like a litmus test, one that, with a three-goal win, returned positive results. Since then, Portland is unbeaten in eight, running their streak to 10 games, in all competitions, with that April 22 result looking more and more like a catalyst as the season goes on.

Now, with home draws in their last two MLS matches, it may be time for another kickstart. And ultimately, there may be no better place in Major League Soccer to test yourself than on Atlanta United’s home turf.

Here is this week’s KeyBank Scouting Report - three things to watch as the Timbers take on the team at the top of the league’s charts:

1. Fun with formations, for both teams

This week, we’ve spent a lot of time talking about Portland’s formations, not only weighing last week’s diamond midfield against the entrenched 4-3-2-1 but also remembering back to the season-opening 4-2-3-1, as well as, in Know Your Opponent, the once-used 4-1-4-1.

Put together like that, it seems like a lot of numbers. And compared to most teams, it is. Most MLS clubs are bouncing between a couple of setups, if they’re changing at all. But it’s not so much that the Timbers have been all over the place this season as they’ve been willing to go all over the place, able to adapt as needed to combat their opponents.

Atlanta, too, has been of more than one mind, formationally, though from a distance, their tweaks appear to be more subtle. The team generally varies between two looks -- a three-center back set, as well a four-man defense -- within which they can play with one or two forwards.

The tricky part, though, is that the team can switch back-and-forth without changing or compromising their personnel. Because right winger/right wing back Julian Gressel can switch seamlessly between positions, United can, essentially, just rotate their personnel clockwise, moving five or six players along a dial to come at you with an entirely new look.

The three different looks Atlanta United have offered teams this season.

Gressel’s versatility may explain why Hector “Tito” Villalba, ostensibly a more talented attacker (13 goals, 11 assists last season), has had trouble reclaiming a spot in the starting XI. It’s also why it’s hard to predict how Savarese will set up his side. Will he place a bet on Gerardo Martino playing his two-front, wingback approach? Or will the formation Atlanta used last week, in their 2-0 win at Columbus, be used on Sunday? In which case, Portland has to be ready to manage the wide threats in United’s 4-2-3-1.

2. Injuries and returns in defense

Who, exactly, is selected to manage those threats takes on a new dimension in the face of the Timbers’ renewed health. According to Savarese, both Liam Ridgewell and Julio Cascante, sidelined for Friday’s U.S. Open Cup match against the LA Galaxy, were fit enough to compete for spots in the 18 for Atlanta. Likewise, Alvas Powell, who hasn’t started a game since May 26, should be in contention at right back, having played 30 minutes against the Galaxy. And finally, Vytas is starting to reassert himself in the fullback conversation, having finished his first 90 of the season with the first team a week ago.

For the first time all season, Savarese should have his whole first-choice arsenal at his disposal, something that explains why the Timbers boss is more confident than most ahead of Sunday’s kickoff.

“I do like the way things are looking,” Savarese confessed, “because we do have a healthy team, right now, that can go there from a weekend where we had to play our U.S. Open Cup game on Friday, not [on] Wednesday. So, we’re preparing for this match in a very big way. We know it’s going to be a big challenge. I think it falls in a perfect moment.”

As we said in Know Your Opponent, Atlanta’s unique challenge may require unique solutions. But with arguably the deepest team in Major League Soccer, Savarese won’t lack for options. Whatever challenges he seems from the league’s top team, Savarese should have the resources to meet them.

3. Nagbe versus Blanco/Valeri

Of course, no discussion of Portland versus Atlanta would be complete without mentioning one of the more talented players to adorn a Timbers uniform. Sunday will mark the first time Darlington Nagbe will line up opposite the Green and Gold, and given how the game’s likely to play out, his performance should play a crucial part.

Atlanta, undoubtedly, will have their share of the ball, meaning Portland’s most likely (but not only) route to three points will be converting on the counter. It’s one of the only ways slower players like Jeff Larentowicz, a rock at the base of midfield, and defender Leandro González Pírez, and all-league performer can be exploited: by making them defend in space; in one-on-one situations. Atlanta’s season-opener against Houston may seem like a long time ago, but it was still a reminder of how much players like González Pírez can struggle when you force them out of their comfort zone.

It will be on players like Diego Valeri or, if he’s positioned as he was against the Galaxy, Sebastián Blanco to exploit those players, although that’s where Nagbe’s influence can help. If he plays with the same defensive awareness that Portland fans remember from the 2015 title run, Atlanta will have an extra layer of insulation to protect their back line. That’s been the case for much of this season. If, however, Nagbe’s defense is more akin to that which, at one point two years ago, led Toronto head coach Greg Vanney to describe him as one of four Timbers “who don’t defend,” Portland could have an advantage through the middle.

Playing centrally for Martino, Nagbe has already established himself as an important part of his new team. And in his first game against his former club, the U.S. internationally will undoubtedly want to play well. But against a team he called his for seven seasons, he’ll face players familiar with both his strengths and weaknesses. How he can harness the positives while offsetting the negatives may go a long way toward determining Sunday’s result.