The one position where MLS is producing U.S.'s brightest prospects

Major League Soccer's 20th season is down to four teams. And when they begin their conference finals on Sunday, there are plenty of intriguing storylines.

Much attention will be paid to the youthfulness and good soccer displayed by all the remaining contenders – the New York Red Bulls, Columbus Crew, FC Dallas and Portland Timbers. And there will be questions asked about the fact that, at a time when the league has imported more star power for more money than ever before, none of the last teams standing have a genuine soccer star on their rosters. They are teams that were built shrewdly, eschewing the high-priced household names and opting for balance instead. And balance beat big names this season.

[ MLS Cup Playoffs: Columbus Crew vs. N.Y. Red Bulls | Portland Timbers vs. FC Dallas ]

But there's a bigger and perhaps more important story that hides along the sidelines. And that's the rise of the American soccer coach. Each remaining team employs a young, homegrown manager, who played in MLS and is either on his first or second professional head coaching job.

New York's Jesse Marsch is 42 and played in the league for 14 years. His last job was as Montreal Impact coach, in its inaugural season. Oscar Pareja, 47, is Colombian but has been in the United States for almost two decades. He spent eight seasons in MLS – 7½ of them with FC Dallas. He then ran Dallas's youth academy before returning to manage the senior team after a stint with the Colorado Rapids. Caleb Porter, 40, built the University of Akron into a juggernaut after injuries ended his MLS playing career and then took over the Timbers. Gregg Berhalter, 42, is the only one to have worked abroad, for Hammarby in Sweden, and is now in charge of the Columbus Crew.

If this dominance by American coaches – or honorary Americans, in Pareja's case – sounds anecdotal and a tad flukey, it isn't.

The final four of managers underscore a larger trend. Seven of the eight managers in the conference semifinals were young and homegrown, which is to say that they either played in the league and hung around or got their coaching start in MLS.

In fact, of the 23 managers employed by an MLS team at some point in 2015, 17 were active in the league as players, and none for fewer than three seasons. A full 15 of them were on their first head coaching jobs in the professional ranks. And 18 managers had never managed elsewhere than in MLS – and of the five that did work in other professional-level jobs, Bruce Arena and Frank Yallop only managed the U.S. and Canadian national teams, respectively.

Porter has an explanation. "There are times where I think it's one of the toughest leagues to be manager in in the world," he said of MLS. "Because ultimately, it's a league of parity and it's a league where you have for the most part pretty equal budgets outside of the Designated Players. And because of that on any given day anybody can beat anyone."

More than that, though, Porter argues, is the many complications beyond the parity mechanisms. It's the tight budget constraints, the endless travel in a short schedule, the differing climates and altitudes.

"Because of that, it's a very difficult league to manage in," Porter said. "You see with a lot of foreign coaches that come, because there's unique challenges that make it difficult. With all of the young coaches that you've seen recently that have come in and done well, they're guys that know the league. They know how to set up and they're not surprised with the travel and all the challenges that go into it. They get it. They're not frustrated, like some foreign coaches that come in."

Pareja agrees. "Major League Soccer is a different league," he said. "It's very unique. Just being part of Major League Soccer [as a player] helps us managers, understanding the culture of the players, the adversity that they face here in America."

It's little wonder then that so many former players won jobs and held onto them – thereby encouraging other teams to hire from within the league. While MLS has slowly begun developing its own talent by aggressively investing in its academy systems, it has become a far more productive pipeline for coaches. Of the 23 coaches employed by MLS in 2015, 14 were 43 years old or younger.

"Now you see the managers grow with the league," Pareja said. "It's a great opportunity for us – the belief that the ownerships and the commissioner have. The people involved in soccer in America just giving opportunities to people who have been involved as players is a good step for us, letting us grow."

There are other factors in the sudden rise of the homegrown manager. Berhalter points to an earlier generation of role models who demonstrated that American coaches had the knowhow to thrive in MLS and then passed on their knowledge.

"We have to thank our predecessors and thank our mentors, guys like Bruce Arena and Bob Bradley and Dave Sarachan and Bob Gansler – guys that paved the way for us," he said. "I'm sure a lot of coaches in the league now have learned from them. Overall, it's a good statement that you see young coaches in this league learning from their predecessors and then going on to be successful."

That earlier generation of American managers laid the foundation by doing good work when they were still in the minority. In MLS's inaugural season in 1996, just four of the 13 managers employed by the 10 teams were American-born. In 1997, it was four of 12. The next year, when the league expanded to 12 teams, it was six of 16. But Arena won the championships those first two seasons and Bradley the third.

Certainly, American managers in those days didn't have the benefit of a stable league to grow into. Nor, consequently, could the clubs choose from a great deal of qualified applicants. As such, the league developing American coaching talent as it matured was sort of natural.

But MLS front offices nevertheless deserve praise for enabling that process to play out by giving an awful lot of managers a shot at a young age. Ben Olsen was just 33 when D.C. United handed him the reins in 2010. Jason Kreis was 34 when Real Salt Lake put him in charge in 2007. As has often been the case in MLS, both transitioned almost straight from the field to a coaching job – most first spend a few seasons as assistant.

"The fact that we're all sort of from the same generation I think speaks volumes for how far this country has come," Marsch says of the four remaining coaches in the playoffs. "There's a new generation of coaches that I think has learned a lot from being players, from having access to the sport and to this league, and now we've all kind of grown up."

This all bodes well for the sport in the U.S. as a whole. The quality of your coaches ultimately dictates your future fortunes as a soccer country. Look at any elite footballing nation, and you'll find a vast network of strong coaches improving players of all age levels. But that has to start organically, and does so at the top, not the bottom. And homegrown coaches finding plenty of work in the upper echelons of their industry will create opportunities lower down as well.

Over the next three Sundays, as the culmination of the MLS season unfolds, the men along the sidelines likely won't get much of the attention, but that they're there at all is a big win for MLS – and, by extension, American soccer.

Leander Schaerlaeckens is a soccer columnist for Yahoo Sports. Follow him on Twitter @LeanderAlphabet.