Rarely has the Cascadia Cup matchup had such playoff implications.

Share story

Interim Sounders coach Brian Schmetzer racked his brain, stared off into the distance with vacant blue eyes, and thought aloud.

Schmetzer has taken part in the Seattle-Portland rivalry as a player and a coach. He can vividly recall who he sat next to in the Kingdome (Steve Buttle). He can tell you where he met with Adrian Hanauer when the owner of the then-USL Sounders offered him his first head-coaching gig (Tully’s Coffee on 19th, across the street from St. Joseph’s Church).

But try as he might, Schmetzer could not recall a bigger Sounders-Timbers regular-season game than the one that will take place on Sunday at Portland’s Providence Park.

Sunday

Sounders FC @ Portland, 2 p.m., ESPN

There was the Western Conference semifinal series edged by the Timbers back in 2013, but that was another beast altogether. There was Clint Dempsey’s home Sounders debut earlier that year, when more than 67,000 packed into CenturyLink Field to watch the hosts win 1-0.

“That was a big game. 67,000 — that’s massive. But as far as importance in the standings is concerned, to my knowledge and my recollection, yeah,” Schmetzer said. “We’re nipping at their heels, with a game in hand. It’s two rivals. There’s a lot to that.”

The rivals are separated in the conference standings by just a single point­ — and the San Jose Earthquakes.

Portland entered the weekend in sixth place — edging the seventh-place ’Quakes from the final playoff berth only by the goals-scored tiebreaker — but having played one more match than San Jose and Seattle.

The Timbers have lost four of their last five league games, the latest a comprehensive defeat to the Sounders at CenturyLink last Sunday. Eighth-place Seattle is unbeaten in five matches since Schmetzer took over from longtime coach Sigi Schmid last month, a streak maintained by Nicolas Lodeiro’s last-minute, game-tying goal on Wednesday against the Dynamo.

“I’ve been adamant that this team is in a good space,” Schmetzer said. “The locker room, the chemistry — they’re in a really good spot. I believe in my team. … They’ll come after it. They know what’s on the line.”

What’s on the line is what’s known in soccer parlance as a potential six-point swing — win Sunday, and you not only give yourself a boost in the standings, you’ll also kneecap one of your closest challengers.

The Cascadia Cup is still in play, as Seattle could pull into a three-way tie with Portland and Vancouver in the regional competition with a victory.

Portland coach Caleb Porter astutely pointed out before last weekend’s match that this series rarely produces stand-alone results. In recent years, the Timbers and Sounders have used these rivalry games either as a springboard or anvils tied around their ankles.

With less than 10 matches remaining in the regular season and both squads fighting for their playoff lives, momentum gained or lost on Sunday afternoon could have significant implications in September and October.

Sunday’s match is also Seattle’s first since the club revealed Friday that Dempsey is being evaluated for an irregular heartbeat.

The veteran forward scored twice in that 3-1 win against the Timbers at CenturyLink, again proving a reliable foil to Seattle’s biggest rivals. His absence — and the weight of the reason behind it — will hang heavily over Providence Park.

“It’s obviously all in our minds, losing one of your best players,” Schmetzer said. “But again, these guys are good pros. My messaging will be: ‘We still have a job to do. Let’s make it to the playoffs. Clint comes back, he can play with us in the playoffs. Those story lines are still left to be told.’ ”

On the other side, Fanendo Adi is set to return to the Timbers’ starting lineup. Adi scored Portland’s goal in stoppage time last weekend — despite having started on the bench for missing the team flight amid rumors of a rift with club management.

They rarely skimp on the drama, Sounders-Timbers matches. Rarely, if ever, are they also as heavy on playoff implications.