Article by Ben Griffis

Marcelo Bielsa is one of the most influential managers in football history. While not being a serial trophy winner, he has inspired many managers—several are even former Bielsa players—to adapt his philosophy, such as Mauricio Pochettino, Diego Simeone, Mauricio Pellegrino, and Jorge Sampaoli. Countless of his former players who are still playing or recently out of the game, such as Fernando Llorente, Javi Martínez, and Dimitri Payet, have discussed how much Bielsa taught them about the game.

Bielsa also helped revolutionize match preparation among managerial teams, relying on video and data analysis to prepare opposition tactics and analyze his players’ performance to improve them as footballers. He reportedly analyzed every tactic used in the Championship in the 2017/18 season to show “exceptional talent” for his English work permit.

The primary tactic Marcelo Bielsa uses is a 3-3-1-3, shown in the image below. His system is incredibly demanding in all phases of play. He requires his players to transition from attack to defense as quickly as possible and relentlessly press the opposition. Once winning the ball back, players must transition to attack quickly, with all but the defenders joining in on the attack high up the pitch.

Because of the system, Bielsa’s teams are not only strong at the back, but very aggressive in attack. Since joining Leeds, Bielsa has won over supporters and non-supporters alike. I was curious if we could see any noticeable effect on data (outside of league points) of Bielsa’s style compared to previous managers. I downloaded Championship data from football-data.co.uk, which includes many variables, but I focused specifically on the margin which teams outshot their opponents, both when playing at home and playing away from home.

This was a simple calculation. For each home (away) game, I took the number of shots the home (away) team took and subtracted the number of shots the away (home) team took. So, for any given home game, the calculation was [home team shots – away team shots]. I looked at shots because the number of shots a team has indicates both the attacking tactics a manager installs and how solid the team’s defense is. A team solid at the back faces fewer shots than a poor defending team. Conversely, taking more shots means that the team not only has a fair amount of possession, but that they are actively progressing the ball up the pitch to use that possession. Compare this style with a Pep Guardiola-type tactic which aims to dominate the game through possession and hold on to the ball to look for perfect opportunities.

I made this calculation for every match, and averaged the numbers out by team for 5 seasons, from 2015/16 to 2019/20. Over this time frame Leeds had 5 managers, Steve Evans, Garry Monk, and Thomas Christensen for about a season each, and Paul Heckingbottom for the second half of the 2017/18 season. Bielsa took over at the start of the 2018/19 season. So, while we could compare each manager, I’m mainly focusing on comparing 2 seasons of Bielsa-led Leeds to 3 seasons of non-Bielsa Leeds.

Over the course of these 5 seasons, 37 different teams played in the Championship. Some for all 5 seasons (Leeds, Brentford, etc.) and some for only one (Sunderland and Newcastle). Below is an image of the Tableau visualization. Follow the link to play around with it yourself.

Each number is the average difference of shots for/against for each team in a season, separated by home and away games. A positive number means the team averaged more shots than their opponents (blue highlight), and a negative number means a team averaged fewer shots than their opponents per game (red highlight). Given that home field advantage has been proven to exist (see this paper), it is thus unsurprising that there are far greater positive numbers when playing at Home and far greater negative numbers when playing Away.

Now let’s look at Leeds’ data. Over the five seasons, they recorded Home numbers of 0.96, 0.00, 0.61, 9.96, and 9.04 respectively. From 2015/16 to 2017/18 Leeds were barely outshooting their opponents at home and ranked near the bottom of the 24 teams in each season. However, in 2018/9 and 2019/20—Bielsa’s tenure—they ranked first in the league, 3.13 and 2.04 above the second-best team in those respective seasons. This jump is wildly abnormal, as no team exhibits a jump of around 9 more shots than their opponents like Leeds did 2017/18 to 2018/19.

Looking at away outshooting numbers is much the same. Leeds recorded -1.83, -3.26, -3.48, 4.78, and 5.65 over the five seasons. The team was getting worse each season until Bielsa took over, and again we see an almost 10-point improvement from being outshot by 3.48 on average per game to outshooting the opposing home team—on their own turf—by 4.78. Bielsa further improved the team in 2019/20. While most teams are outshot away from home by 2 to 4 shots per game, Leeds under Bielsa act like an average home team even while playing away. The numbers are truly staggering, but perhaps unsurprising for Bielsa’s disciples.

Here are a few outputs from a quick ANOVA analysis of Leeds in JMP:

Source	DF	Sum of Squares	Mean Square	F Ratio	Prob > F
Season	4	2245.1826	561.296	13.6891	<.0001*
Error	110	4510.3478	41.003
C. Total	114	6755.5304

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Source	DF	Sum of Squares	Mean Square	F Ratio	Prob > F
Season	4	1844.3130	461.078	8.3741	<.0001*
Error	110	6056.6087	55.060
C. Total	114	7900.9217

From the ANOVA results, we can say with 95% confidence that Bielsa did in fact have a large effect on Leeds’ attacking and defending phases. Leeds’ league positions over these seasons were 13th, 7th, 13th, 3rd, and 1st respectively. Leeds immediately went from being a mid-table team to entering the promotion playoffs and finally winning the league and promotion back to the Premier League under Bielsa, and the significant ANOVA results show his effect.

This quick analysis shows Bielsa has in fact had a significant and noticeable effect on Leeds United’s ability to outshoot opponents and take away their opponent’s home field advantage. This has led to Leeds being crowned champions of the Championship in 2019/20, recording many strong results in the 2020/21 Premier League thus far, and winning over plaudits and Leeds fans alike. Bielsa is one of the most influential managers in football history, and I personally can’t wait to see how far he can take Leeds. His 3-3-1-3 tactic is incredibly flexible, able to quickly change from fluid attacking to structured defending at the drop of a dime, with little transition time. This tactic is no small part of his success.

Hader image source.