TORONTO -- To get a sense for the significance of the Seattle Sounders' first MLS Cup championship, consider the collective mental state of their opponent ahead of this weekend's rematch.

Prior to last December, the Sounders had been tagged as perennial playoff underachievers. The consistent regular-season success, huge crowds they attracted to CenturyLink Field and U.S. Open Cups were all well and good, but without a league title, those accomplishments had begun to ring hollow. The club needed a championship to validate all the rest.

Those are sentiments Toronto FC can identify with as it seeks its own inaugural MLS Cup on Saturday at BMO Field (4 p.m. ET, ESPN/WatchESPN). TFC is on the brink of the greatest single season and first treble in MLS history, having already lifted the Supporters' Shield and Canadian Cup trophies; yet it also knows that without one more win, all those previous victories will be looked upon differently.

Expectation has weighed heavily on Toronto's shoulders this postseason. Tempers flared throughout its conference semifinal series against the New York Red Bulls, culminating in a brawl in the tunnel at halftime of the second leg. The Columbus Crew pushed the Reds to the wire in the East finals, and in truth, the favorites were fortunate to have gotten through.

Seattle, meanwhile, coasted to a second straight MLS Cup appearance. Some of that is due to the relative weakness of the Western Conference. Some of that, too, is thanks to the absence of the suffocating pressure that had characterized so many of its previous playoff appearances.

"To a lot of people in the fan base and inside the organization, and to me personally, it felt like a weight was lifted," Seattle owner Adrian Hanauer told ESPN FC this week. "The expectations were so high. It just felt like that pinnacle of Major League Soccer had finally been reached. It burst the balloon of pressure, I think, which has made it more fun for everybody involved, which I think is a good thing for having even more and more success."

A second straight title might not mean as much, symbolically or emotionally. You never forget your first championship, the long sought release after years of pent-up frustration.

That might not necessarily be a bad thing: The Sounders have played with greater freedom in the past few months, more stylishly, with contributions coming from all over the field.

"As I've observed some of the playoff soccer this year, I've sensed some teams feeling that intense scrutiny and pressure, and not playing as loosely as they'd maybe want to," Hanauer said. "We've struck the right balance during this run."

A second straight title would also exalt the Sounders into select company in league history. Only D.C. United in 1996-97, Houston Dynamo in 2006-07 and the LA Galaxy of 2011-12 have previously gone back-to-back.

"Good organizations with great culture and infrastructure and resources and great people set themselves up to succeed consistently," Hanauer said. "For me, that's probably the biggest source of pride with this club. Those pieces of the puzzle are in place, and that leads to opportunities like Saturday.

"To the current definition of what the Sounders are and whether they're a dynasty or not a dynasty, that doesn't interest me as much as consistent quality year after year."

His players were more willing to open up about what a victory on Saturday would mean in a big-picture sense.

The Seattle Sounders can become just the fourth team in league history to win back-to-back MLS Cups. ESPN Illustration

Forward Will Bruin played for Houston when it fell to the Galaxy in both the 2011 and 2012 finals. He has an acute understanding of just how difficult it is to reach this stage in consecutive years, let alone triumph once there, and said that these Sounders stack up favorably with those Galaxy teams that his Dynamo so struggled against.

"This Seattle team is probably the deepest team I've ever been a part of," Bruin said. "There have been a lot of injuries and adversity throughout the year, but we've had guys that stepped up and played big, big minutes. The camaraderie and the ability that we have at every single position throughout the field -- first [string] and second and third -- you can go down the roster and it is very good throughout."

Goalkeeper Stefan Frei, last year's MLS Cup Most Valuable Player, senses how close his team is to reaching rarefied air.

"I think we're at the point now where we're starting to get in that elite level of clubs in MLS," Frei said. "The league, and people from the outside, are starting to notice that we've reached the playoffs every time. Even though we might be a young team compared to some of the original ones, we're starting to fill that cabinet with trophies. I think being able to achieve something like what the LA Galaxy did, by winning back-to-back, would cement us in that elite class, because I have tremendous respect for those squads.

"We sense that opportunity, and how that would cement us in that elite class."

It's an opportunity more than an obligation, which separates Seattle from where it stood a year ago -- and perhaps more importantly -- from its host on Saturday.

Having finally broken through in 2016, these Sounders' legacies are secure. Toronto can only imagine how freeing that must feel.