Jurgen Klopp's Liverpool have lost three games in a row at Anfield. For so long, Anfield was a fortress as they went on a run of 68 games without losing at home. But with the Kop still standing silent as the coronavirus pandemic continues to necessitate games without fans, and following defeats to Burnley, Brighton and Manchester City, the fear factor is at an all-time low.

Speaking before playing Pep Guardiola's City on Sunday, Klopp said: "Our situation is not talking about supporters being in or out because we know how much they can help. We knew that always and for a long time we could ignore that, at least results-wise. Now we can't in the last few weeks."

Liverpool went on to lose that match 4-1. "For many years we were not able to win here, hopefully next time we can do it with people," Guardiola said. "Anfield is so intimidating. Anfield is always impressive, but with people it is much more."

Liverpool are far from an isolated case in the Premier League this season. Of the 17 sides still in the top-flight from last season, only five teams (Chelsea, Aston Villa, Southampton, West Ham and Tottenham Hotspur) have seen their home form improve when playing in front of empty stands, compared to their pre-coronavirus form surrounded by fervent support.

- Stream ESPN FC Daily on ESPN+ (U.S. only)
- ESPN+ viewer's guide: Bundesliga, Serie A, MLS, FA Cup and more

"It is quite clear without supporters at the stadium, the home team doesn't have the advantage with the supporters behind their shoulders," Everton manager Carlo Ancelotti said when asked by ESPN. "It's quite simple, the teams had more difficulties at home than away -- this is the only reason."

But for each team and player, the impact is different. It's prompted talk of testosterone levels, behavioural shifts and motivational shortfalls. It's also potentially cost managers their jobs. With fans still locked out of the grounds in the pandemic era, we spoke to managers, players, psychologists and statisticians to find out whether playing at home is no longer an advantage.

Additional reporting by Lewis Holman, Mark Ogden, James Olley, Rob Dawson, Eduardo Fernandez-Abascal and Sam Porskamp

What the statistics say

In short, the data show both a "levelling" of home-away advantage and a swing in disciplinary trends. ESPN's Stats and Information Group analysed 288 Premier League games pre-lockdown from the 2019-20 season, and then the 317 matches since the restart (the remainder of 2019-20 and the 20-21 season so far). The resulting stats saw a drop in goals scored at home (from 1.5 to 1.4 pre- and post-lockdown) and an 18% increase in away goals after lockdown.

Away teams have also come away with better results: home wins have decreased by 2%, but away wins are 26% up from pre- to post-lockdown. Away team yellow cards have also decreased from an average of 1.9 per game to 1.5 per game in front of empty stands, even as fouls committed have stayed roughly the same. This also speaks to referee pressure, which we analysed in June.

The "impact" of empty stands

"Home and away is different, not like it used to be," Manchester United boss Ole Gunnar Solskjaer said in December. "It's a different sensation now playing without the fans behind the goal at the Stretford End -- they normally score a goal for us." The same is said for other intimidating stands, like Liverpool's Kop end or Crystal Palace's Holmesdale Road Stand.

"The intimidation factor is taken away from the opposition," Michael Caulfield, one of the UK's leading sports psychologists, told ESPN. "To a degree, they are almost preseason-like friendlies with nobody there."

When the Premier League returned on June 17, after the first lockdown, the stands remained empty. Some supporters were allowed back in over December in various grounds -- numbers were dependent on government regulations relating to the severity of the COVID-19 outbreak in that part of the country -- but the numbers were capped at 2,000 per game. Even though there were still swathes of empty seats, the players felt the benefit.

"Unfortunately these times are hard for everyone and of course we'd love to have the supporters back because we know they would be a really big help for us, especially at Anfield," said Liverpool's Fabinho. "If they had been here for the games against [Manchester] United and Burnley, I'm sure the results would have been different with that support. Even when we had 2,000 fans here for the games against Wolves and Tottenham, we could feel the big difference that it made."

Liverpool have been hit hardest by the "empty stands effect," but Brighton, Newcastle and Sheffield United's home form has also disintegrated without fans. Liverpool's form also marries with their injury crisis as their three first-choice centre backs are all absent with long-term injuries and the squad is battling "mental fatigue," as Klopp puts it. They've won 10 of their 16 homes games since lockdown -- winning an average of two points per match at Anfield -- compared to last season's remarkable record of 100% until the season was put into hiatus.

"Anfield without fans is just Anfield; Anfield with 60,000 Liverpool fans chasing a 3-0 deficit against Barcelona literally rocks with noise and encouragement," Caulfield said.

"Taking the crowd out of it is a huge detriment to performance; it doesn't frighten the opposition, and it has leveled a lot of things up. The data proves that. Taking that out of it has leveled things to an extraordinary degree."

Sean Dyche's Burnley were the team who broke Liverpool's unbeaten record at Anfield, when they won 1-0 there on Jan. 21. When asked by ESPN what he felt were the reasons behind a growing trend of teams winning fewer games at home, Dyche also pointed to the eeriness of empty grounds.

"The most obvious thing is the home crowd," Dyche said. "Certain crowds, certainly the Liverpool crowd who stick with their team a bit longer if things aren't going well -- there was that old saying of the crowd sucking the ball into the Kop end."

Dyche also pointed to some clubs where they may be benefiting from not having fans. "Obviously there's a handful of clubs where the home crowd can be effective for the opposition, as the home crowd can be more demanding of players than others -- that can go against the home team sometimes -- what kind of season and form they're having," Dyche said. "Generally speaking, home crowds make a big difference."

West Ham, sixth in the league, have benefited the most from having empty stands -- they've won 29.73% more points than prelockdown. Aston Villa, Chelsea and Southampton have also seen an increase in points picked up at home postlockdown. There are other factors here, of course: Villa have markedly improved on last season's form, while Southampton have also taken strides forward under Ralph Hasenhuttl.

Since Thomas Tuchel took over at Chelsea, they are unbeaten in their two home games, drawing 0-0 against Wolves and then beating Burnley 2-0. In previous manager Frank Lampard's last match in charge against Luton Town, there was a banner at the Shed End that read "In Frank We Trust: Then. Now. Forever." The absent fans still wanted to show their support for Lampard. Sources close to Lampard told ESPN he felt he would have got more time had Stamford Bridge been full every week, though their record actually improved at Stamford Bridge without fans, with Chelsea winning 20% more points from their home matches postlockdown than they did before the pause.

Arsenal's record is much the same with and without fans: they have picked up 2.23% fewer points at home postlockdown, than before last season. But sources told ESPN that Mikel Arteta feels his work at Arsenal has been made more difficult by the absence of fans. The disconnect between the team and the supporters became really bad under previous manager Unai Emery, and Arteta feels he has largely been robbed of the chance of rebuilding that relationship. There's also a view from sources near the club that the squad is mentally fragile and would benefit significantly from fan support to get them through difficult moments in close matches.

"We know that home form is going to be vital for our success and we have to change that immediately," Arteta said in December after picking up 13 points from their first 10 league matches. "If we want to have any hope of doing something important and relevant this season it has to be by winning the games at home."

Jose Mourinho, the Tottenham manager, has also seen a difference in the FA Cup experience. His Spurs side traveled to eighth-tier Marine in the third round and though they had supporters peeking through their garden fences at the game, he feels the empty stands have robbed the competition of its uniqueness.

"The FA Cup is a special competition that even with a full stadium, normally weak teams would take much more supporters than in the Premier League," Mourinho said when asked by ESPN about the differing trends in home advantage.

"In the Premier League, I have to admit that it's one thing to play with full stadiums, and another to play with empty stadiums.

"I believe that has an impact in some of the results. Let's just give an example. We were losing against Chelsea 1-0, we were playing much better in the second half than first half. The last 20 minutes the team started pressing a lot and being closer. I believe, I believe that stadium full could make an impact on the team and I think this happens in every stadium. So the public makes a difference, I believe so."

Dyche feels that "broadly speaking, home fans do have a say in how their team operate and that's the most likely thing that's affecting home and away form this season," but he has also looked to the effects empty stands are having on his players, with psychologists and statisticians finding testosterone levels are impacted, concentration affected and players unable to draw on fear as impetus when the grounds are empty.

The effect it has on the players

Klopp's Liverpool have experienced some lopsided scores this term. They had the 7-0 win at Crystal Palace, but also the 7-2 defeat at Aston Villa back in October. That heavy defeat was in the midst of a spate of high-scoring games up and down the Premier League (Manchester United lost 6-1 at home to Tottenham while Leicester won 5-2 at Man City) and back then, Klopp put this down to the players' wavering concentration levels.

"The audience, or the crowd, they sharpen your focus -- that's normal. And you have to do that yourself constantly, but it's no excuse," Klopp said.

The experience has been jarring for Klopp's players, and their silent Kop.

"It's difficult because you don't realise how much fans influence game plans, like with momentum and the sounds you can hear... I miss the fans so much," Trent Alexander-Arnold told Ian Wright in December. A player from another top club told ESPN they are struggling to find their usual urgency late in a game when chasing a key goal. They saw the team slipping into sideways passes in the final throes of the match whereas before, with fans, they'd have been shouted at for playing conservatively and would have gone route one.

Dyche also turned to previous scientific studies on a difference in testosterone levels in players as another contributing factor to the widespread dip in home form.

"There was a test years ago -- football and rugby -- in testosterone levels and home players have a higher testosterone level because of the backing of support, feeling of the home crowd," Dyche said. "If you're talking about small margins, small margins amongst 11 players and subs -- that adds up."

The players' emotional behaviour has also changed in behind-closed-doors matches, according to a study published in journal 'Humanities and Social Sciences Communications' by Michael Leitner and Fabio Richlan.

The study looked at the effect "geisterspiele" (ghost games) had on players, staff and officials through their own "Analysis System for Emotional Behaviour in Football." Using their own criteria and scoring system, they video analysed 20 RB Salzburg matches in the Austrian Bundesliga and found "the absence of supporters has a substantial influence on the experience and behavior of players, staff and officials alike."

Research showed an increase in "Fair Play behaviour" (good sportsmanship) and referees becoming less involved in "emotional situations" (arguments, altercations, disagreements) on the field. They saw players becoming "less carried away with longer-lasting and extensive 'word fights' and 'discussions.'" Instead, it saw a rise in "self-criticism," with players more likely to reproach themselves rather than others after missing a chance, and "protest," where players would shake their head or gesticulate at decisions, rather than respond verbally.

Caulfield believes the impact of empty stands on players is subjective. Some may flourish without the "threat or fear" of crowds, "but for a lot of players, because they are competitive animals who want to perform well in front of a ground, they find a challenge because they enjoy the thrill of the crowd," he told ESPN. "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.

"The truth is, it's very ugly and that's why we are seeing such evenly matched games. It's very difficult to win, regardless of who you are playing against the pandemic has caused football to change a lot, and for the worse. You can see it in the matches, and I hope this all ends soon and we can get fans back into the stadiums and return to normality."