BEAVERTON, Ore.—The Portland Timbers understand they are in a more precarious position than they hoped for heading into the season’s home stretch.

They also are not inclined to panic.

“We know we’re in a huge dogfight, and we know we have no margin for error at all,” said head coach Caleb Porter. “So it’s going to come down to this performance in the next game and we’ll take it from there.”

That next game is Sunday’s Heineken Rivalry Week matchup with rival Seattle Sounders FC (2:00pm EPT; ESPN), who have climbed within a point of the Timbers – just above the Western Conference red line – and last weekend beat Portland in in Seattle. That loss, Porter admitted, hurt more than most.

“I think it took the guys [and] myself a couple days to get over,” Porter said, after a Tuesday training session he called spirited.

The rematch this Sunday is not mathematically a "must-win," but Porter understands the existing arithmetic:

The Timbers have four home games remaining, and play three of them over the next four weeks … before finishing with three of four on the road.

“If we don’t [win on Sunday] is the season done? No. But it just puts more and more pressure,” Porter said. At the very least, another loss to Seattle make it difficult for the Timbers to control their playoff fate down the stretch.

But the high stakes don’t mean a big shakeup. Unlike last season, when a formation change sparked the Timbers run to the MLS Cup title, Porter said he has no plans to play Diego Chara as a lone holding midfielder in an effort to get more men into the attack. Going with a single pivot does not make sense against Seattle’s mobile attackers, Porter said. Besides, a lack of depth at the wing positions means the Timbers do not have an obvious attacking player to insert in place of a holding midfielder.

In fact, wing players have scored only six of the Timbers 37 goals this season. Fanendo Adi (12 goals) and Diego Valeri (10) have accounted for 59.5 percent of Portland’s goals.

The 2015 Timbers had nine players score goals during its six-game postseason run. This team has had to shuffle its lineup all season because of injuries, international obligations and other absences. And Portland has battled the emotional letdown that comes after reaching the summit, Porter said.

What the coach hopes is that a consistent lineup can translate into more consistent results. Porter is confident his team will respond as it often has when challenged and, last Sunday aside, they've had a strong record against the Sounders, particularly at home. The Timbers are 5-1-2 against Seattle in their last eight games at Providence Park, the most recent win coming in July with a 3-1 victory marked by a brace from Valeri.

“Our challenges started right after we won [MLS Cup]: losing players, managing the cap — then compounded with injuries,” Porter said. “It’s been a challenge, but here we are, still in position [to make the playoffs].”