It’s new territory for Major League Soccer: five teams simultaneously competing for the regional crown.

Starting next week, a maximum number of MLS sides will begin the grueling journey in the group stage of the CONCACAF Champions League, and it’s an unprecedented opportunity for the league to shine in the competition: Nearly one-third of the participating teams come from MLS.

That in and of itself is exciting, to say nothing about the question of whether any of them can one-up Real Salt Lake and actually win the thing.

But first things first. With the LA Galaxy, Colorado Rapids, FC Dallas, Seattle Sounders and Toronto FC all in the group stage, that adds another 30 matches to an already crowded stretch run to the MLS Cup playoffs. These teams will be juggling games like never before.

Before we delve into the nitty-gritty of the CCL (which we’ll do to death here at MLSsoccer.com starting next week), it’s time to take a look at how the quintet’s participation in the tournament will trickle down to the Supporters’ Shield and playoff race. And believe us, CCL will impact both big-time. Here are four story lines to follow:

1. Battle of attrition out west. Yes, we already know that of the five MLS sides in the competition, four are from the Western Conference. But take a look at the current standings in the West.

All four participants are stacked up at the top of the table and each has more points than the East-leading Columbus Crew. And that will make for a fantastic battle atop the conference as each squad does its respective balancing act over the next three months.

Real Salt Lake GM Garth Lagerwey admitted to ExtraTime Radio this past spring that during their run in last year’s Champions League, he and head coach Jason Kreis mapped out on a whiteboard their team’s schedule over the past 12 months.

In seeing the fixture list, they were able to prioritize which games were most important during a crowded time on their schedule — i.e., if the regulars could be rested over certain stretches in order to save them for more important dates on the calendar.

As the four Western powers go to battle during the stretch run of the regular season, it’ll be fascinating to see how Bruce Arena, Schellas Hyndman, Sigi Schmid and Gary Smith rotate their rosters and how they treat certain dates over others — if they do at all.

By the time the sixth and final group-stage game rolls around for everyone the week of Oct. 16, the MLS regular season will be coming to a close and the playoff picture will come into focus. For LA, Dallas, Seattle and Colorado, it’ll be a heavy test of mettle and fortitude.

2. Chance for the opportunistic. With the aforementioned point in mind, it’s entirely possible all four teams will limp to the finish line, whether they’ve secured advancement to the knockout stages of the CCL or not. An extra six games per team — all in midweek — during a busy stretch run is going to take a lot out of these teams, no matter how successful they are.

Who stands to benefit? None other than Real Salt Lake. Their absence from this year’s CCL — and their elimination from the US Open Cup, which they made a concerted effort to win — will work in their favor. RSL have no extra competitions to worry about, plus they’ve still got at least three games in hand over all of the West-toppers thanks to their light league schedule earlier this season when they were making their CONCACAF run.

Yes, they’ve missed Javier Morales terribly, and the absences of Jámison Olave, Kyle Beckerman, Álvaro Saborío, Arturo Alvarez, Will Johnson, Luis Gil and Paulo Jr. due to injuries and national-team call-ups has hurt, too. But Kreis’ gang is one of the best-disciplined, deepest squads in the league. If anyone can get it together in a hurry and make a run at the right time, it’s them. They’ve got a little history in that department.

3. Training ground for TFC. All right, let’s be honest: It will take a minor miracle for Toronto FC to make their first-ever playoff appearance, even if they turn the ship around immediately. They’ve won all of three league games in 2011 and have bled goals at an alarming rate, dead last in the league at nearly two allowed per game and with a shocking minus-22 goal differential.

To expect any kind of consistency from Aron Winter’s group this deep into the season is all just for bonus points. TFC’s manager has added 13 new faces since First Kick and shipped out seven — including two captains — and counting.

But with the playoffs a distant dream at this point, that makes the CCL Toronto’s best chance for redemption. And for a team with Europeans both in management and on the field, there is an understanding within TFC’s camp exactly what continental competition means and how best to balance it.

No one should be surprised if Winter aligns his team to go all-out in Champions League play, especially with two DPs in Torsten Frings and Danny Koevermans who are more than familiar with those high stakes.

The reward for passage into the knockout rounds is redemption for what has been an enormously trying year in Toronto, for both the team and the fans. Starting in 2012, TFC can start fresh with both a new regular season and a chance to progress in the tournament. Maybe by then the growing pains for Winter will be over — and maybe the roster will finally be settled, too.

4. Depth tests. When the group stage kicks off next week, FC Dallas and Seattle will be competing for four trophies at the same time: the Supporters’ Shield, the MLS Cup, the Champions League trophy and the US Open Cup.

That kind of challenge is what vexes even the top European managers, and it’s rare to see even the biggest of the big guys chase them all at once. But with apologies to RSL, perhaps no organization has geared up better for long runs in multiple tournaments than Seattle.

Schmid told MLSsoccer.com just last month that of all his accomplishments this season, he’s perhaps most proud of the performance of Seattle’s reserve team, who only lost their first game in the Reserve League season this past Tuesday.

First-team fringe players and end-of-the-benchers like Lamar Neagle, Servando Carrasco, Mike Fucito, David Estrada and Miguel Montaño have all been able to stay fresh in competitive action. That depth more than anything may give Seattle an edge this fall.

Jonah Freedman is the managing editor of MLSsoccer.com. “The Throw-In” appears every Thursday.