Three tactical trends that are defining the 2021 MLS season

Soccer changes. That’s one of my very favorite things about it. Over time, teams decide to start using one particular tactic or approach. Then other teams start copying it, then it becomes mainstream and then somebody starts using a new approach and the cycle repeats itself.

Sometimes the changes are extremely noticeable – like a global shift towards playing out of the back – and other times they’re much more subtle. From year to year in MLS, the changes tend to fall into that second, more subtle category. Still, a handful of notable league-wide tactical trends have developed this year. By comparing Second Spectrum’s 2021 data with its 2020 data, we can dive into some of the most interesting on-field trends that have popped up across the league this season.

Before we start, I do want to highlight because last season was a strange one, Second Spectrum didn’t collect data from as many games as they have this season. Understandably, they were unable to collect data from the MLS is Back Tournament in Florida, so the sample size from last season is closer to 20 games per team rather than the normal 34 games (plus playoffs). By averaging these stats out on a per-game basis, 2020’s weirdness doesn’t have a major impact here, but I still wanted to mention it.

And coming off Week 23 of the 2021 season, we're at a comparable measuring point to the pandemic-shortened 2020 season duration-wise. Things dovetail nicely there.

Anyways, it’s trend time. Let’s do this thing.

While the back four is still king, playing with three center backs has graduated from being a lowly page in the king’s court to being a legitimate knight sitting at the king’s table. 

In 2020, 22.3% of offensive possessions in MLS featured some kind of a three-at-the-back shape, per Second Spectrum’s tracking data. In 2021, that percentage has risen to 32.5%. That’s a major increase!

At this point in the season, every MLS team has used a three center back shape in possession – and seven teams have used a three center back shape in at least 50 possessions per game. Last season, only three teams hit that mark.

While Brian Schmetzer’s shift toward using three center backs in Seattle may be the most high-profile shape adjustment, LAFC, D.C. United, Chicago Fire FC, the Colorado Rapids and Atlanta United have all used a back three in possession significantly more this season than last season.

There are a wide variety of reasons why MLS teams are starting to use a back three more often in possession – a new coach’s tactical preference, personnel changes, a specific tactical matchup, wanting to be like the cool kids, et cetera. But one thing is certain: MLS is all aboard the three center back train.

If back threes are in, then passing is out. In 2020, MLS teams attempted 946 passes per game. This year? That number is down to 919.2 passes per game.

It’s not an insane decline, but a nearly 30 pass-per-game dropoff is significant. Teams have become less interested in controlling possession and breaking opposing defenses down with passing.

They aren’t spending as much time passing in the buildup phase or in the progression phase, which are the two offensive phases Second Spectrum classifies as only happening against an organized defense.

One potential reason passing numbers are down from 2020 to 2021 is the amount of time the ball is in play is lower this year than last year. Effective playing time, which Second Spectrum defines as “the time during a game where a ball is considered live, excludes when the ball is out of play or dead,” has dropped from 56.9 minutes per game in 2020 to 55.3 minutes per game in 2021.

As the age-old saying goes, with shorter games comes fewer passes. Okay, no one actually says that. But, hey, there’s no reason we all can’t start saying it.

Shorter games may be having an impact on passing, but they’re not hurting high pressing. So far in 2021, the number of team presses in the final third (read: high pressing) is up slightly from last season. Teams are averaging 1.2 more high presses per game in 2021 than they did in 2020.

To get a bit more specific, not only is MLS high pressing more this year, but more of the 27 teams are high pressing at a higher rate this year compared to last year. In 2020, six teams averaged at least 12 high presses per game. In 2021, eight teams are hitting that mark – and four teams are high pressing more than 2020’s most active high pressing team (Sporting Kansas City).

Now, it’s important to note the COVID-19 pandemic’s effect on last season likely impacted high pressing (and most other parts of soccer, too). Still, as MLS teams continue to spend and their squads continue to get deeper, it would make sense to see high pressing continue to trend upwards across the league over the next few seasons.