That Oakley Cannonier became a cult hero for his role in Liverpool’s 4-0 win over Barcelona to move onto the Champions League Final shows how even the smallest margins are a byproduct of detailed planning. The 14-year-old ball-boy, handpicked by Liverpool academy coaches to work the match, was briefed by video analysts to return the ball back to Liverpool players as soon as possible after it went out of play as they found that Barcelona tended to switch off in crucial moments.

Thus, after Trent Alexander-Arnold played a ball off Sergi Roberto for a corner, Cannonier immediately threw a new ball back to Liverpool’s right back. Alexander-Arnold then lulled Barcelona’s defenders into turning off before playing a cross to Divock Origi for Liverpool’s 4th and deciding goal, with Gerard Pique and Marc-Andre ter Stegen the only two defenders to react. 

“I left the ball for the corner and then saw the space,” explained Alexander-Arnold of the move. The Liverpool right back even outsmarted both managers with Jurgen Klopp and Ernesto Valverde admitting that they didn’t see what happened as they both turned their back after the ball initially went out of play. Valverde explained that Origi had already scored by the time he looked up, with Klopp, the mastermind of the quick corner, adding that he didn’t even realize who delivered the ball. The polar reactions from each side revealed the differing interpretations of a single, deciding moment: Klopp described the 20-year-old Alexander-Arnold’s play as a “genius moment.” On the other side in Spain, it was called “the corner of shame.

Although it was another corner kick from Alexander-Arnold taken days before against Newcastle that made history. His service to Virgil van Dijk in the 13th minute meant that he and left back Andy Robertson became the first Premier League duo to reach double-digit assists in the same season. Alexander-Arnold would add another assist later in the match, putting both he and Robertson at 11 for the domestic season, with 13 in all competitions. No team in Europe relies upon their fullbacks for creativity in the final third more than Liverpool. The height of their impact came in a 5-0 win over Watford in which both players provided all the assists in the game. Robertson said following the match that if he gets two assists, he expects Alexander-Arnold to get three assists and outshine him.

“We started a small competition last season to see who could have the most assists,” said Robertson of his relationship with Alexander-Arnold. The duo are displaying their influence during an era when the role and value of the position are undergoing a significant re-evaluation. Fullbacks have been perceived as the most valuable position on the field for over a decade, with their importance as box to box players relied upon to attack and defend symbolized through record-breaking transfer fees. But Alexander-Arnold has been with Liverpool since he was six years old, and Liverpool signed Robertson in 2017 for just under $8 million. The price and subsequent development of Robertson is probably Klopp’s most impressive in his time with the club. 

Despite their fullbacks’ attacking aggression, Liverpool still are tied for the stingiest defense in the league. Of course, that balance is a result of a team-wide effort with their energetic pressing both a form of defense and attack. But there is also an analytics-driven duality within the team: as Liverpool push the limits of modernity with their press, there is a world in which how Robertson and Alexander-Arnold create chances no longer exists.


With the early developments of analytics in soccer, we are waiting for that “Moneyball” moment of an analytically-inspired upheaval of foundational assumptions of the game. Alexander-Arnold and Robertson combine for over nine crosses per game. The average European side sends in 18.6 crosses per match, with a conversion rate of 1.6%. Crossing makes sense on the surface: put the ball into a dangerous area to find a teammate. It is how we watch teams desperately try to claw back a goal towards the end of matches. It is also how many of us grew up playing the game. Why cross? Because it’s what teams have always done.

“The net effect of crossing is a negative for all teams in all studied competitions,” concluded a 2014 report studying the impact of crossing using regression models. According to another study in 2015, a Premier League side would need to hit 67.46 crosses in order to score 1 goal (just over 20% of goals in the league came off crosses). A mathematics professor in Prague found that a team would score 0.393 more goals per game if they never crossed the ball, totaling 15 extra goals per season. Yet there are also nuances in how we define a cross, not just in the act but the action that it creates in opposition defenses. Premier League consultant Garry Gelade observed that in order to truly measure the effectiveness of crossing, one needs to also look at the sequence that occurs up to 6 seconds after the ball is played into the box. Studying the second ball brought the conversion rate up to 2.2% per cross, with the back post cross more successful than a near post cross with a 7.6% conversion rate.   

There are also cultural and stylistic elements of crossing. Unsurprisingly considering their philosophy, Barcelona averaged the least amount of crosses during the time of study with just 11 per match. There is a perception that sending in a cross to advance the ball from deep is an individualistic, brute force approach compared to the majesty and beauty of long passing sequences filled with team movement and quick, one-touch thinking. February 9th, 2014 is held in infamy as the day that David Moyes’ Manchester United set a record by crossing the ball 82 times in a 2-2 draw against Fulham. It is seen as the match that sums up Moyes’ lack of imagination in taking over the club.

Moyes defended his style after that match in explaining that getting wide and crossing the ball is “in the genes” at United. But it is also that focus on crossing and winning second balls, resulting in a lack of control, that is the biggest adjustment for any foreign manager into the Premier League. One answer to that problem is to try to tame and regain control of the second ball. Yet Robertson, Alexander-Arnold, and Liverpool have fully embraced the madness, finding logic in the uncontrollable. With Liverpool up 1-0 to Barcelona but down 3-1 aggregate in the second half, and before his famous corner kick, Alexander-Arnold received the ball on the right wing with space. He lost the ball to Ivan Rakitic before winning it back from Jordi Alba and sending in a deflected cross for Gini Wijnaldum’s goal. That moment wouldn’t have been categorized as a successful cross under traditional methods due to the deflection, but the intent behind the pass - to attack a disorganized defense after a turnover - was deliberate and rehearsed. Maybe it isn’t about the individual skill of crossing, but the ability to deliver a cross in the right moment.