Soccer is an evolving thing, both on and off the field. Chants are thought up and then adjusted and changed and reborn over the years, as are rivalries and tactics and rules and the game itself. Everything is always sort of shifting in one direction or another, and at every moment it's hard not to feel like you're at the apotheosis of history, that what you're witnessing somehow matters more, or is more revelatory, than what's come before it. And that everything coming after it is just commentary.

That's not the way of things, especially tactically. There is no "one formation to rule them all."

But I will say this: "Modern soccer" - the game as we know it - really took shape from 1988 through 1995, when three crucial things occurred.

First, Arrigo Sacchi took over at AC Milan and then the Italian national team, all the while emphasizing the importance of defensive compactness and the utility of "banks of four" when defending. While there are minor heresies to be found throughout the world, much of the game's current blueprint was drawn by Sacchi.

Second, in 1992 FIFA adjusted the back-pass rule, speeding up the game after the incredibly dire 1990 World Cup.

And finally, in 1995 most of the world changed from "two points for a win" to "three points for a win."

Those latter two events incentivized attacking play from a strategic view, while the first set the parameters of how coaches would achieve their ends tactically.

And into that maelstrom MLS was born.

****

The earliest years of MLS proliferated with teams playing some version of Sacchi's 4-4-2, which we'd recognize today as a "flat" 4-4-2, or if the lineup and run-of-play pressures are right, an "empty bucket" 4-4-2. Industry was provided by the central midfield, wide midfielders bent in a ton of crosses, and the most creative player was usually the second forward. Defenders were rarely hybrids, even when there was space to exploit.

If that was the typical set-up, then the disruption thereof was provided by Bruce Arena's D.C. United team -- and if you were around to watch that group you probably wouldn't feel too bad arguing that, to this day, it was the best team in MLS history. There's no league Hall of Fame yet, but once there is at least two guys (Marco Etcheverry and Jaime Moreno) from that group will be in on the first-ballot, while a bunch of others (Jeff Agoos, Raul Diaz Arce, John Harkes, Roy Lassiter, Carlos Llamosa, Eddie Pope, Tony Sanneh, Richie Williams) will have arguments for an early inclusion as well.

But United didn't shoot out of the gates in 1996. They struggled until Moreno came on board in midseason, giving Arena the ability to complete his 4-4-2. He morphed it into a diamond midfield -- which, up to that point in soccer history, was a set up used purely in South America -- that had a pure creator at the tip (Etcheverry) and a mobile and rugged, yet equally creative forward (Moreno) playing anywhere in the final third.

With those two freelancing, it was up to the rest of the squad to provide the structure. Williams was an especially undervalued piece of the puzzle, bringing a Didier Deschamps-like engine and tenacity in ball recovery, while Diaz Arce's commitment to running the channels drew defenders away from the pure creators.

Like all diamonds, it suffered from a lack of width. So D.C. adopted the truly modern solution of having the fullbacks overlap high and hard, often overwhelming teams with sheer force of numbers. It wasn't always balanced since Agoos didn't get as far forward as Sanneh, who was a converted attacker learning right back. But it didn't have to be balanced. It just had to be compact, and ruthless, and efficient, and winning.

D.C. under Arena -- and later under Thomas Rongen, who was smart enough not to mess with a good thing -- were all of those. Between 1996 and 1999, they won three MLS Cups, two Supporters' Shields, a US Open Cup, a CONCACAF title, and the Copa Interamericana, setting the standard for the entire league.

Everybody was looking for their Etcheverry and Moreno. But you couldn't just be another United. You had to figure out how to beat them.

****

The best counterattacking team I've ever seen in MLS was probably the 2011 LA Galaxy. If not them, then it was definitely the 1998 Chicago Fire, who were an expansion team -- and the only MLS club besides Arena's United to win an MLS Cup in the 1990s.

Bob Bradley -- who was Arena's assistant at United for two years -- was the boss of that Chicago team, and like his mentor, he built his squad around the talents of a fiery No. 10 (Peter Nowak) and an underappreciated, ball-winning defensive midfielder (Chris Armas).

Unlike Arena he opted for a 3-5-2, which was rapidly falling out of favor in the late 1990s. Liberalization of the offside law had made the sweeper's job next-to-impossible, while the onset of the 4-2-3-1 at France '98 made playing three central defenders something of a tactical folly.

But MLS was, obviously, a few steps behind Zidane's France back then. And so Bradley relied on Nowak and Armas to strengthen the spine. But the brains of the operation was sweeper Lubos Kubik. The fire would play in a low block to encourage deep turnovers and open field to run into, and somehow always manage to get the ball onto Kubik's deadly left foot.

He'd spray long passes up the flanks, putting the ball into the stride of various wingbacks who would either cycle the ball to Nowak, or whip in a cross to forwards Ante Razov, Josh Wolff, Frank Klopas or Jerzy Podbrozny.

Chicago won the Cup in '98, and stayed in contention for several more years. But as Kubik, Nowak, Armas and the rest aged, the depth of their importance became clear: They could not be replaced like-for-like, and the Fire eventually morphed into a 4-4-2 team.

****

Both teams had imitators at the turn of the century, with Kansas City and the MetroStars in 2000, the Miami Fusion in 2001, Sigi Schmid's LA Galaxy in 2002 and the great New England Revolution teams from 2002 through 2007 playing predominantly in the 3-5-2. It would take a while until there was another great diamond 4-4-2 team -- that'd be Dominic Kinnear's San Jose Earthquakes/Houston Dynamo mini-dynasty from 2005 through 2007, followed soon thereafter by Jason Kreis' Real Salt Lake group.

More than formation, though, the tactical choices MLS coaches seemed to make following the success of those early United and Fire teams were more about getting speed on the flanks and a creator underneath a targetman. Some teams called this a 4-4-2, while others got adventurous and called it a 4-2-3-1, and still others called it a 4-5-1. Some of them worked, but most of them didn't.

Why not?

Well, because one of the hardest things to do in all of sports is complete an attacking pass at speed, and if you're asking your fullbacks to overlap but not just bend in hopeful crosses, you're ipso facto asking them to connect attacking passes at speed. You're also asking your wide midfielders to defend better and run more. And you're asking your defensive midfielder to do more work spraying the ball from side-to-side. And you're quite possibly asking your No. 10 to be more of a No. 8.

Suddenly, the most important dimension any team could have was a defender-occupying center forward, a Brian McBride-type who could push the entire backline deeper by being goal-dangerous on crosses, available in half-spaces from the run of play, and creative with the ball on his foot and runners to pick out.

While McBride was the archetype, Brian Ching was arguably the most successful MLS version of the role. He had a hand in all three major titles for Kinnear's San Jose and Houston teams, and his intuitive understanding of how to release clever, mobile, hybrid attackers like Dwayne DeRosario or Landon Donovan into space gave his teams a creative flexibility that others mostly lacked.

In the 1990s it could be said that the creative impetus came mostly from the midfield while center forwards were mostly just asked to score goals. By the middle of the '00s those responsibilities had shifted. Not all the way, mind you. But enough to make the game look drastically different in MLS. And everywhere else.

****

The final few years of the '00s were mostly variations on a theme, with the 4-4-1-1 of Guillermo Barros Schelotto's Columbus Crew notable both for its beauty and effectiveness, and the straight 4-4-2 of the 2010 Colorado Rapids for its lack of style and effectiveness.

The first real challenge to what had become a 4-4-2 orthodoxy came in 2011 with Sporting KC and their 4-3-3. It was a paradoxical set-up in that it was a throwback (the 4-3-3 is not a new formation by any stretch) that had come back into vogue thanks to Barcelona and Spain. It was also a paradox. Because of the association with Barca, the 4-3-3 was considered by many to be the choice of the soccer aesthete.

But Sporting played it like a hammer hitting a nail.

Nobody sent in more crosses or contested more aerials in the first three years of this decade. They won most possession battles with their high pressure, but they were routinely near the bottom of the league in length of possession.

Give credit to head coach Peter Vermes. He internalized the attacking lessons of the early MLS teams (speed on the flanks & get those fullbacks forward!) while applying the philosphies of Sacchi and Cruyff to his defensive scheme, then revved everything up to the Nth degree. They were compact, they pressed high and hard, and they were pragmatic.

They also won, which, of course, always spawns imitators. Today, we see teams around the league attacking with wingers, applying high pressure for large swathes of time, and aiming cross after cross after cross at the back post. This is especially potent when the guy at the back post is a Kei Kamara-style target winger who can physically dominate the usually smaller fullbacks tasked with marking him.

However, while other teams have adopted Sporting's front-foot posture, KC themselves have become a bit more worldly in how they use their midfield and wingers. And even though they're now a better, more technical team with the ball, they actually possess it less than they did in their "grab you by the throat and choke you for 90 minutes" heyday.

Because the thing with high pressure is that if it's not all aligned just so, you can beat it with a single through ball. And MLS is now littered with through-ball artists who conjure up memories of Etcheverry, Nowak and Valderrama.

Sporting's success does not mean the 4-4-2 has died or even gone out of style. It's just had to evolve.

Nowhere has that evolution been more beneficial than in LA, where Arena -- yes, him again -- from 2011 through 2014 shifted from a flat 4-4-2 to what folks took to calling a "Y" midfield. It's called that because if you look down upon the midfield during the run of play, the spots the four midfielders occupy look like the letter Y: The d-mid at the base of the Y, the box-to-box midfielder at the fork, and the two wide midfielders advanced, but not all that wide.

The success of the Y is based upon the ability of the wide midfielders to instantly swap roles between "creator", "goal-scorer" and "decoy," and their willingness to do so. It's a more complex role than the way the typical wide midfielder is used, and asks more in possession than pure wingers like those in the 4-3-3, or even certain 4-2-3-1s are usually able to give.

Like all other formations, it's only as good as the players playing it. If you have Donovan, Robbie Keane, Marcelo Sarvas and Juninho to throw out there, your formation is going to solve more problems than it causes.

****

So where does that leave us now, in the league's 20th season? Sporting are leading the league in points per game in their 4-3-3, and they are one of 14 teams, by my count, playing primarily in either a 4-3-3 or its close cousin the 4-2-3-1 this year. The 4-4-2 has, in some ways, finally been usurped as the formation of choice in our league.

For now, anyway. The principles that Sacchi drove home a quarter-century ago and that D.C. painted the league with for the first four years, still apply no matter what formation you choose: Stay compact in defense; use your fullbacks to create attacking width; transition at pace; get the ball on the feet of your best chance creator, no matter if he's a forward, a No. 10, a winger, or a center back.

Do what works, and do what wins. Try to be a little entertaining along the way.

Everything else is just commentary.