Real Salt Lake's lineup up in the air as they prepare for final match of 2015

Every soccer league in the world introduces a layer of unpredictability, but none do it with quite as much pizzazz as MLS.

Take, for instance, fixtures between the LA Galaxy and the Portland Timbers this season. On June 24, the Galaxy smashed the Timbers 5-0 at the StubHub Center in one of the most lopsided games in all of MLS this season. Three months later, the Timbers marched into that same stadium and beat the Galaxy 5-2. The crazy thing? The team the Timbers thrashed had Steven Gerrard and Giovani dos Santos in the XI. Those two hadn’t even joined the lineup yet on June 24.

Realistically, every team flies partially blind into every match. Sporting Kansas City had that message delivered to its doorstep on Wednesday when the last-place Colorado Rapids dropped them 2-0. The Rapids have been in the cellar for nearly the entire season. SKC is fighting for a playoff spot. So it goes in MLS.

For that reason, Real Salt Lake’s visit to CenturyLink Field this weekend is no easy contest to call. RSL has been eliminated from the postseason for nearly two weeks, but that certainly didn’t stop them from beating CSD Municipal at midweek to join the Sounders in the CONCACAF Champions League quarterfinals.

The intrinsic law of MLS is that anybody is beatable on any given day. That goes double when you’re not entirely sure how the other team will array its starting lineup.

One thing the Sounders do know is that metronomic defensive midfielder Kyle Beckerman won’t be on the field. The national teamer picked up a prohibitive yellow card for a leg sweep on Mauro Diaz in the team’s 1-0 loss to FC Dallas last weekend. The ironman will therefore give way to a fresh face in that holding No. 6 role, which creates a huge divot in the midfield the team will undoubtedly struggle to replace on the fly. You don’t simply replace a Kyle Beckerman.

How RSL lines up everywhere else is just as undecided. The team has nothing to play for on Sunday aside from pride, meaning RSL Head Coach Jeff Cassar could well decide to throw some of his younger players into the inferno to see how they handle the heat.

Javier Morales went 90 minutes against Municipal on Tuesday, which means the 35-year old Argentinian creative midfielder went 180 minutes in the span of four days. Morales is probably the most consistently productive central attacking midfielder in MLS history, producing 45 goals and 75 assists in his nine years with RSL. He’s gotten more consistent as he’s aged, too, with double digit assist totals and at least eight goals in each of the past three seasons.

Morales might play, but can his aged legs take three 90-minute matches in the span of a week? We’ll see. If not, Luis Silva has tucked into that spot in place of Morales in the past. Silva went 63 minutes against FCD and wasn’t in the lineup for Municipal. Sometime to watch for.

Tricky attacker Joao Plata is another question mark. He was questionable for the Municipal match with a left adductor strain, and he ultimately wasn’t fit enough for the 18. Was Cassar keeping the dangerman out of harm’s way in order to start him this weekend? Or was Plata so injured that he won’t have nearly enough time to recover in time for this weekend? More smokescreens rising from the Wasatch Range.

If Plata can’t go - he’s been training, for whatever that’s worth - expect to see a front line with some combination of Juan Manuel “Burrito” Martinez, Devon Sandoval, Olmes Garcia, Jordan Allen and Sebastian Jaime. The latter only went 12 minutes against Municipal and should be fresh. Garcia only went 12 minutes against FCD and didn’t play against Municipal. Allen, meanwhile, has impressed out wide in his first real season after inking a Homegrown deal.

While the attack isn’t quite up to the standard of its Fabian Espindola-Alvaro Saborio peak from a few years ago, it’s still dangerous. Just ask the Sounders players who watched RSL ring up two goals in the opening 20 minutes of a 2-0 loss in Sandy, Utah on Aug. 23.

As for the back line, don’t be surprised to see something similar from the FCD game. Jamison Olave could well play, but considering he’s 34 and played 90 exhausting minutes on Tuesday, he might be tipped to be replaced by either Aaron Maund or Elias Vasquez, who performed admirably against FCD despite the midfield being at times overwhelmed by the opposition’s numbers in attack. The one player you can bank on playing is keeper Nick Rimando, perhaps the best keeper in MLS history. Give him a few more inches of height and Tim Howard would’ve had a difficult time holding him off for first team USMNT duty.

The most dangerous team is the one with little to lose. That, in this case, is RSL, and that’s only intensified by the relative uncertainty their XI poses entering the match. Seattle can qualify for the postseason with a win, and while it can still push into the playoffs with a draw or loss, it’ll have to pray FC Dallas beat San Jose and the LA Galaxy take care of Sporting KC.

It’s unlikely SKC and San Jose both win while Seattle loses or draws, but as we’ve established, this league is an unpredictable thresher. Anything can happen on any given day.