Determining the surest path to Major League Soccer success is tricky business; A league in ongoing evolution makes it so.

It’s like raising children. What works in creating the most precious little kindergartener won’t work as that kid turns 11 or 12. What compels best behavior for pre-teens probably won’t do the job when they start driving.

So it is with MLS. The growth curve will eventually level out, and it has probably already begun doing so. And yet, it’s still tricky business for now, because what worked in 2005 isn’t what works in 2015. When we cut down to the bone of Ws and Ls here, we’re mostly talking about three areas of evolution: what kind of player cuts it in MLS, how rosters are constructed and what kind of manager tends to be most effective.

Tuesday, the Chicago Fire hired Veljko Paunovic, the man who worked wonders with the Serbian under-20s, which recently lofted FIFA’s Under-20 World Cup trophy at the expense of more celebrated sides. Well done, sir!

Paunovic does have experience in MLS, although only the proverbial cup of coffee. He made 17 appearances for the Philadelphia Union in 2011. The Union’s was the last of 11 uniforms Paunovic wore over 18 professional years.

The Yugoslavian-born former midfielder, now 38, certainly isn’t the highest profile of recent managerial hires. That goes to Patrick Vieira, the towering figure who presided regally over Arsenal’s midfield for some fantastic teams around old Highbury.

Vieira finished at Manchester City, where club leaders recognized his abilities and wisely folded the Frenchman into their youth development efforts. Earlier this month, the City Football Group named Vieira to replace Jason Kreis at New York City FC.

SEE MORE: Vieira appointment shows City has yet to learn from the Lampard fiasco.

The initial reaction on these recent hires – and, admittedly, my reaction – was that some lessons need re-learning. Again and again, it seems. In this case, that the best chance at MLS managerial achievement means handing the whistle and chalkboard to someone whose teeth were cut in the league, or those who have invested significant time here, at least.

It’s that elemental familiarity that matters, finding someone who won’t be undone by the cold water plunge of the league’s unique quirks and peculiarities, not to mention a salary structure and set of player acquisition mechanisms that is completely, well, foreign to most foreigners.

The foursome of clubs still alive in this year’s MLS playoffs are directed by American born-and-bred Jesse Marsch, Gregg Berhalter and Caleb Porter, and by Colombian Oscar Pareja. Pareja joined MLS in 1998 and hasn’t lived beyond the States since. Ironically, he appears to be the most passionate believer in the upside for American soccer talent; his story of building the FC Dallas youth system is getting plenty of sunshine, and deservedly so.

More to the point, Pareja is the first non-American manager since Englishman Gary Smith in 2010 to make Major League Soccer’s “final four.” (We’re counting Sigfried Schmid as “American;” born in Germany, “Sigi” Schmid came to this country as a small child.)

SEE MORE: FC Dallas and the birth of MLS 3.0.

So while Juan Carlos Osorio, Wilmer Cabrera, Marco Schällibaum, Hans Backe, Aron Winter and other “sexier” foreign hires have come and gone to varying degrees of stalemate or outright collapse, a few good old Yankee Doodle Dandies are getting the business done. (Obviously, quite a few Americans have come and gone, too.)

Ruud Gullit was the most notorious of the foreign sexy man hire. Gullit is the fabulously talented Dutchman who failed so fabulously in his managerial walk-about with Los Angeles. The course correction was hiring the most successful American-born manager ever to walk our Earth, Bruce Arena.

So, buy American, right?

Well, maybe. That’s where this MLS-in-evolution thing comes in. That’s why, after some reconsideration, taking a chance on a Paunovic or a Vieira has some merit, too.

Nelson Rodriguez is making the critical calls around Toyota Park outside Chicago now. Rodriguez spent 14 years in MLS, mostly in various jobs at HQ in New York. He’s a sharp guy, and he should know as well as anyone what works and what doesn’t.

Paunovic does represent the bold choice. That doesn’t make him the best choice; only time will tell about that. But Rodriguez didn’t fall back on someone safer, someone with previous MLS managerial experience. That’s what Chicago (Frank Yallop) and Montreal (Frank Klopas) did before, never mind that both coaches had tumbled ingloriously from their previous posts.

The downside to hiring Paunovic is that someone like Kerry Zavagnin, who has now interviewed twice for the Fire position, doesn’t get his chance. Zavagnin has served faithfully under Peter Vermes at Kansas City, and will hopefully get his opportunity at one of the new MLS addresses. Or maybe at Chicago, if Paunovic doesn’t, er, pan out.

Zavagnin would have been a safer choice, although not necessarily the better one. Will Paunovic work as Major League Soccer rounds itself into MLS 3.0? It’s not a strong position to take as an analyst, but the most honest answer is, “We’ll see.” We barely know what MLS will look like in 2016, much less what it will look like as a 24-team league by 2018 or thereabouts.

I mean, the Galaxy or the Sounders might find a couple more star-men that they really, really want over the next couple of years – which means the league is likely to invent new rules to see that it happens. Seriously, the league’s salary structure and acquisition devices remain a work in progress. So do the primary club targets. If US Open Cup and CONCANCAF Champions League become more attractive objects of desire, it may alter the way clubs divvy up the roster dough. Either way, club approach will vary.

Teams like Dallas and Vancouver are demonstrating that building inexpensively around youth is a viable alternative. New York and Columbus, the Eastern Conference teams still alive, are built on the cheap, too, although the MOs around Mapfre Stadium and Red Bull Arena look a little different, a more assorted mix of young and old.

Marsch and Berhalter certainly look like great coaching fits. But maybe they wouldn’t be the best choices for Yankee Stadium, where managing big ego and big politics from City Football Group make that job a different jar of pickles altogether. Just ask Kreis.

Maybe Berhalter or Marsch would be miscast at clubs where youngsters will need patient, almost fatherly tutelage. Perhaps Pareja wouldn’t work at Toronto, another address where high-dollar figures will continue to be a heavy weapon. We don’t know.

Some clubs are going to demand bottom line success. That makes a guy like Dominic Kinnear, an old school 4-4-2 guy whose teams achieve through locker room accountability and blue collar ethos, a solid choice. Ben Olsen, who looks safe at D.C. United despite an apparent plateau, has a team of grinders that look a lot like 11 Ben Olsens from back in the day.

But the owner or club decider who demands a more stylistic approach – think Portland Timbers or Sporting Kansas City – may need a coach of different stripes.

Perhaps the point is this: Increasingly in MLS there is room for diversity of approach. That goes for playing style, for personnel acquisition and development and for managerial design. It looks that way in 20-team MLS, so it stands to reason that a 24-team MLS will accommodate similar diversity, if not even more.

The key that fits the lock here: finding the right man for the specific job. Is he a builder? An organizer and taskmaster? A disciplinarian? A motivator? A tactician who can take what someone else has built and get them over the hump?

And there’s one more critical element: the man has to want the job.

SEE MORE: Difference between MLS and NASL models creates a worrying arms race in the second division.

This is where it probably does pay to buy American. People raised through MLS want to be here. For lots of American coaches, a place like Chicago would be their dream job. That may or may not be the case with Paunovic; we’ll see.

Is it really the case with Vieira? Again, we’ll see … although it’s hard to imagine that someone revered in his playing days in France, England and Italy doesn’t have bigger ambition than whuppin’ the New England Revolution or Orlando City SC, etc.

If you’ve been around MLS a while, you probably remember the Gullit fiasco. Bottom line, his heart wasn’t in it. This was a weigh station, a stop en route to something “bigger and better,” apparently. There’s room for diversity in MLS, but not room for that kind of mess. Bold choices may reap pure gold – but there’s always someone willing to pawn off some fool’s gold, too.