Real Salt Lake and the Seattle Sounders are set to square off on Saturday night for the second time this year – another Western Conference battle on another warm, summer night, you might assume.

Think again.

Over the past four years, the RSL-Seattle rivalry has developed into one of the strongest in MLS. Sure, it doesn't have the geographical undertones and sheer passion the Cascadia rivalry boasts, or the edge and history of the Rocky Mountain Cup. But what it does showcase is the most consistent teams in MLS, and two that are always ready to have a go at each other.

Here are three reasons why RSL-Seattle is the best MLS rivalry no one's talking about:

1. The teams are good

The trophy cabinets speak for themselves. Whether it's RSL's MLS Cup title or the Sounders' three straight US Open Cups from 2009-11, not to mention impressive showings from each in the CONCACAF Champions League, there's sufficient evidence to see that any meeting between these teams is going to be high-quality.

It's a claim backed up the record books, too. There has been only one losing record between the two teams since Seattle entered the league in 2009, RSL's 11-12-7 showing in that same year. And as you might recall, RSL still ended up winning MLS Cup in 2009 anyway. Both teams have qualified for the playoffs every year since 2009, with RSL going 66-43-35 in regular season play over that period compared to Seattle's 65-36-40.

In addition to their strong records, neither side has been lacking on the field. Jason Kreis & Co. have implemented one of the most attractive styles of play MLS has seen in recent years, while the Sounders have fielded some of the most electrifying players in the league and shown themselves very capable of putting on a show for their raucous home crowd.

Simply put, these are two of most consistent teams in MLS over the past few years, and even if the goals aren't always there, you can almost always be sure that this is one matchup that will always produce some high-quality soccer.

2. They've produced some of the most dramatic playoff games in recent memory

A natural evolution of the two teams' on-field success in the past few years is that they've come together for some memorable playoff meetings, beginning with their first postseason encounter in 2011.

Kreis' side put on a show in the first leg of their Western Conference semifinal clash, with Álvaro Saborío striking on either side of halftime and Ned Grabavoyadding one late in a 3-0 rout. But Seattle mounted a comeback, scoring twice within the first 16 minutes of the second half in the return leg, only to fall just short. But they would avenge their loss in 2012.

After a 0-0 first leg, this time in Seattle, a game marked by some of the best goalkeeping the MLS playoffs will ever see – from Nick Rimando and Michael Gspurning alike – the scene shifted to Rio Tinto Stadium. Again, the two sides looked destined to remain scoreless, until Mario Martínez conjured a magical late strike to send Seattle through and the home crowd disappointed.

3. And they are almost inseparable

That oh-so-memorable playoff series in 2011? That was the only occasion since the very first meeting between RSL and Seattle that either team has won by more than a goal. Seattle's 2-0 win over RSL on March 28, 2009, the Sounders' third-ever game in MLS history, is the only time a regular-season game between the two teams has been decided by two goals or more.

Part of what makes a rivalry is the fierce competition between the lines, including three straight 0-0 draws in 2012.

Only RSL's 2-1 win earlier this year broke the dead-even 3-3-6 record between the two teams (regular season and playoffs), giving the Claret-and-Cobalt a slight advantage in the series heading into Saturday's game.

And given the way both teams have been playing recently – RSL are 3-1-1 in their last five games in MLS play and Seattle are 4-1-0 – it should be another close, hard-fought meeting.