RSL won the Western Conference semifinal series last season by a two-game aggregate of 3-2.
The Sounders have not advanced in the playoffs since 2008. But they finished third in the West during the regular season with 56 points, only one behind Real Salt Lake.
While top-seeded San Jose is favored to emerge as the conference's representative in the MLS Cup, RSL and Seattle are legitimate challengers, which adds to the intrigue of this early-round series.
Asked why the Sounders are one of the league's top teams, Real Salt Lake coach Jason Kreis said, "It's a combination of everything.
"They have two very good forwards in [Fredy] Montero and [Eddie] Johnson, they have midfielders who can contribute to the attack … and they have a back four that's very organized. They are an extremely well-coached team as well."
But Seattle could be without Johnson for Game 1 of the series.
After scoring a franchise-record 14 goals, Johnson was injured in the season finale against the L.A. Galaxy on Sunday.
According to Johnson, he suffered a slight hamstring strain. But on the Sounders' official report, the injury is called an adductor strain.
Either way, he is listed as questionable for the playoff opener.
Johnson "adds a little different dimension to their team," Kreis said. "He's a dangerous player I know from playing with him many eons ago. But he's very athletic with very good speed and he's good with his head on the end of things. He's been their go-to guy."
If Johnson can't play, Kreis knows it will impact Seattle's attack, which has been unable to score against Real Salt Lake in three matches during the season.
"If they are missing him," Kreis said, "they are missing a key component. Hopefully, we could take advantage of it."
Even without Johnson, however, Seattle is capable of beating RSL especially in front of another fanatical home crowd.
The Sounders finished third in the Western Conference despite a nine-game winless stretch midway through the season that could have ruined their chance to reach the playoffs.
Along with Johnson, Montero is the leader of the league's fifth-ranked offense. He scored 13 of Seattle's 51 goals this year.
Meanwhile, midfielder Mauro Rosales finished with a franchise-record 13 assists. He was Major League Soccer's Newcomer of the Year in 2011.
"I think this team definitely has what it takes to make a run at the championship," Schmid told the Seattle Times. "There is enough quality on the field, enough quality on our bench and the desire is definitely there."
In goal, Real Salt Lake faces Michael Gspurning, who allowed only 15 goals in 21 games during his first season with the Sounders. His goals-against average (0.73) was third-best in MLS.
RSL vs. Seattle
A game-by-game look at the Real Salt Lake-Seattle season series:
Real Salt Lake 1, Seattle 0
May 12, CenturyLink Field
Fabian Espindola scored in the 50th minute and RSL handed Seattle its first loss in more than a month. Luis Gil assisted on Espindola's goal, which was the first scored against the Sounders in 321 minutes.
Real Salt Lake 0, Seattle 0
July 4, Rio Tinto Stadium
RSL dominated most of the match but could not score and settled for the draw, snapping a three-game losing streak. A crowd of 20,363 watched keeper Nick Rimando record his 57th career shutout.
Real Salt Lake 0, Seattle 0
Oct 17, CenturyLink Field
RSL gets for another draw, despite a one-man advantage for 60 minutes. Seattle goalie Michael Gspurning made two scrambling saves to rob Chris Schuler and Sebastian Velasquez in stoppage time.