"The crowd is their feedback -- you think of the greatest stand-up comedians of the moment, their feedback is the laughter or silence from the crowd. Football is the same, the cheer, roar and the excitement.
"How many times have you heard: the crowd kept us going and scoring in front of them is the best feeling ever. That is not there anymore, don't be surprised if now and again if levels dip because there is nothing coming back to you."
Is the same thing happening elsewhere in Europe?
Economics professors (Carl Singleton, James Reade both from the University of Reading, and Dominik Schreyer, WHU, Otto Beisheim School of Management) have been analysing home advantage across Europe. Their paper "Eliminating Supportive Crowds Reduces Referee Bias" saw home advantage decrease by 3% in games played without crowds, which included analysis of matches dating to 2002.
In the Dutch Eredivisie -- which has seen the biggest swing in favour of the away teams with home teams winning on average 55% of home matches prelockdown, to 38% postlockdown -- Feyenoord manager Dick Advocaat told ESPN before their trip to Ajax in January: "As a football player, you want to play in a full stadium, and the passion and emotion that comes with it. But the fact that there is no audience in the Johan Cruijff Arena is to our advantage: you have to be honest about that."
For those teams further down the league like FC Emmen -- dead-last in the Eredivisie, with no wins from 21 games -- they are lamenting the lack of their 12th man. "We miss the audience, 100 percent," FC Emmen manager Dick Lukkien told ESPN. "If you look at the past years, that was a perfect collaboration. We are now the victim of that. I think it cost us a lot of points. The lack of the audience is very important to us."
In the Bundesliga, Borussia Dortmund's home record is poor this term compared to last prelockdown. Before the break last season, Dortmund were undefeated at home. Postlockdown, they have lost six of 14 home matches in the league.
The players miss their fabled "Yellow Wall" of support in the Sudtribune. Interim boss Edin Terzic told Sky after the win at Leipzig on Jan. 9: "Sure, we miss our fans. Whenever we take to the pitch they sing 'Let's go Dortmund, fight and win,' that's the slogan we work hard for."
Dortmund sporting director Michael Zorc told Bild following the Mainz draw on Jan. 16: "We miss the Südtribüne. When we have fans behind us, it just helps us extremely."
In La Liga, Real Madrid have lost a total of eight games across all competitions this season and four of those have come at home, all against so-called "lesser" teams (losses to Cadiz, Alaves and Levante in La Liga and the 3-2 Champions League defeat to Shakhtar Donetsk). ESPN sources say there's a recognition in the club that there's a huge difference between playing in front of a full house in the Santiago Bernabeu and at an empty Alfredo di Stefano stadium at the training ground on the outskirts of Madrid.
The players' routines have changed too. Take big European games at the Bernabeu: you'd usually get thousands of fans greeting the team bus on its arrival at the stadium prematch. Now, playing at Valdebebas, the team don't even get on a bus at all; they just stroll over from the residence nearby after the team meeting. "I don't like playing without fans," Real Madrid boss Zinedine Zidane said in June.
Over at Barcelona, one source told ESPN that playing in stadiums like Osasuna, which are traditionally considered very tough and claustrophobic, is a lot less stressful without fans. (Six La Liga sides have more home wins than draws and losses this season, with three of them -- Barcelona, Atletico Madrid and Real Madrid -- joining Sevilla in being as good away from home.) Though the players do miss the supporters.
"It's horrible to play without fans, it's a very ugly sensation," Leo Messi said in December. "Seeing no-one [in the stands] is like a training session, and it is very tough to really get going at the start of a game.