Portland is led on offense by Argentine Diego Valeri, the league MVP last season, who had 10 goals and 12 assists this season. Sebastian Blanco added 10 goals and 11 assists. Diego Chara provides the toughness in midfield.

Atlanta United and Portland have met once in each of the past two seasons. Both were 1-1 draws.

This season, the Timbers bunkered and counter-attacked against Atlanta United at Mercedes-Benz Stadium. On defense, they proved very difficult to break down June 24. Larrys Mabiala gave the Timbers an early lead before Julian Gressel equalized just before halftime.

It also was the game in which Atlanta United midfielder Darlington Nagbe left with an adductor injury that forced him out until September and forced Martino to revert back to the 4-2-3-1 formation he most most of the 2017 season.

The teams continued playing their respective styles most of the rest of the season with different results.

Using the 4-2-3-1 for most games in the remaining months, Atlanta United led the league in goals (70) and finished tied for the second-most points in league history (69).

Using either a 4-2-3-1 or 4-3-2-1 formation, the Timbers continued to try to frustrate opponents and finished with a goal-difference of plus-6 and the fifth seed in the West (54).

Things have changed in the postseason.

In an effort to minimize mistakes, Atlanta United has become a team that is focusing on defense first. It is 3-1-0 in the postseason with just two goals allowed. Part of that focus is Martino’s decision to switch back to a 3-5-2 formation that plays to the strengths of Nagbe.

“We essentially played with wing back and five in the back in the first leg, and we scored three goals, and we could’ve had more, so we have been able to go between systems throughout the season,” Atlanta United goalkeeper Brad Guzan said. “I think that is a strength of ours being able to go from one system to another.”

Red Bulls coach Chris Armas said the 3-5-2/5-3-2 can be frustrating to break down.

“Their structure 5-3-2, again, it wasn't a secret, when you play like that ... it's just tough for us to really attack the spaces that we're used to,” he said.

If there is one player on Atlanta United who knows the Timbers, it’s Nagbe. He played for the Timbers from 2011-17, helping them win the MLS Cup in 2015. He requested a trade after the 2017 season, and Atlanta United acquired him in one of the biggest trades in MLS history.

And if Portland manager Giovanni Saverese has won a title in Atlanta before, when he led the New York Cosmos past the Silverbacks in for the North American Soccer League title in 2013.

"We're not done yet," Portland defender Zarek Valentin told mlssoccer.com. "We want to go into Atlanta and make it as tough as possible and hopefully get one more win.

"It's going to be tough. They're a very talented team from front to back. They're very good with the ball. The crowd brings it, as well."