The Premier League season has started with a goal-fest.

Sunday's chaos, with Aston Villa scoring seven against Liverpool and Tottenham beating Manchester United 6-1, capped a mind-boggling start to the 2020-21 campaign.

Goals are being scored at the highest rate in the English top flight for 90 years.

There is one obvious difference this year - the absence of fans. Is that the cause of the goal rush? If not, what else could it be? BBC Sport takes a look...
Goals, goals, goals - what the stats say

There have been 144 goals in 38 games this season. That's 40 more than after the first 38 games of the 2019-20 campaign.
There have been an average of 3.79 goals per game - the highest in an English top flight since the 3.95 goals per game in 1930-31.
11 of the 38 games this season have featured at least five goals (29%). That's the highest percentage in a season since 1960-61.
On Sunday, Liverpool became the first reigning champion to concede seven goals in a game since Arsenal in 1953.
On average there have been 4.05 'big chances' per game this season - the highest average since Opta began recording the statistic.
The average number of shots per game has decreased compared to previous seasons but shot conversion rate has increased dramatically to 16.1% from 11% last season.

'You might concede three but still win'

Everton and England defender Michael Keane says the issue of more goals being scored in the Premier League has been talked about by players.

"It's been mentioned," the 27-year-old said. "Obviously there are loads of goals going in and you might concede three, but in the Premier League at the minute you might win 4-3 or 5-3."

Asked whether it could be due to a lack of fans in stadiums, Keane said it was "a mixture of things" including players "having to isolate due to Covid".

"Players aren't having the same amount of training. I think maybe fans not being in the stadium might make a bit of a difference," he added.

"It might give the strikers a bit more freedom to try things they perhaps wouldn't if they felt there was a bit more pressure there with the fans

"As a defender it's not like in the Premier league we have forgotten about clean sheets and we don't want them."
'A little piece of chaos has been dropped in'

Speaking on BBC 5 Live's Monday Night Club, journalist Rory Smith suggested the absence of fans in stadiums was a factor in the "strange start to the season".

"It is a little piece of chaos that has been dropped in," he said.

Presenter Mark Chapman said: "I have spoken to cricketers and other athletes this summer [who have competed without crowds] and it is easier for your mind to wander if there is not a crowd to keep your concentration up.

"Alan Shearer and Jermaine Jenas were talking about the adrenaline you get from a crowd. Maybe that adrenaline drops slightly when the crowd isn't there."

One first-team coach at a Premier League club told BBC Sport a lack of fan pressure was "definitely" affecting decision-making.

He said it is taking away the sense of tension players feel around build-up play near their own goal and is also reducing the intensity and demand they feel for aggressive defending.

To help with this, the team in question are going to train more regularly at their stadium, with their more intense 10 v 10 training sessions held there rather than at their training ground.

Carlos Carvalhal, manager of Portuguese side Braga and the former Sheffield Wednesday and Swansea boss, said: "The absence of fans in big clubs with big pressure on them reduces the focus and concentration of players.

"Fans open up your senses, increase the intensity of your muscular reaction. It has a huge influence in the head of players, I would say even 20%.

"The influence of fans of big clubs normally has a clear effect on opponents too as they feel more pressured. Without them it is 11 v 11 with a ball and a ref - everything balances out."

Sports psychologist Michael Caulfield said: "Football is a game based on threat, fear, and that has disappeared with no fans in the stadium.

"Plus, teams like Sheffield United or Crystal Palace, with a loyal set of fans that back them up as they feel lucky to be part of the Premier League, miss the arousal of the fans in the same way Freddie Mercury would miss the audience."
'Awful defending and terrible goalkeeping'

Former Premier League striker Chris Sutton disagreed that the absence of fans explained the number of goals.

"The standard of defending in the Premier League is awful and there is terrible goalkeeping," he said.

"It is not because there isn't a crowd there - that is not the reason. The standard of defending has dropped dramatically.

"There is an argument to say if there was a crowd at Aston Villa and [Liverpool goalkeeper] Adrian, after his first mistake, how much worse could he have been with a crowd there?"

Ex-Manchester City and England defender Micah Richards agreed.

"It is a cop-out," he said. "Even if fans were there, the scores would have been the same. I have been with Man City and it was a same score [6-1 against Manchester United]. There were fans there then."

So what else could it be?

The thoughts of the former players are clear, but is it really a coincidence that Liverpool, Manchester United, Manchester City, Leicester and others have forgotten how to defend at the same time?

This season is one like no other with players having little time off in the summer and minimal pre-season training.

"Elite athletes are reacting differently to before the pandemic," Caulfield said.

"Even though the standard of play is very high, there is a genuine mental cognitive fatigue at the highest level despite the lockdown - that was not a relaxing time."

Some were hampered more than others. Manchester United, for example, had only 34 days - and one pre-season friendly - between last season ending and this one beginning.

A lack of preparation and tiredness could be factors, but the opposite may also be true.

Tottenham, who have already played eight matches in all competitions this season, may have found their groove early thanks to more playing time, whereas United are still searching for rhythm, having played only five.

The number of penalties has increased dramatically too, with games including penalties up 22% from last season partly because of new handball laws.

Defenders could also be allowing more openings as they defend tentatively in an attempt to stay clear of the punishment of video assistant referees.

The absence of fans, individual mistakes, tiredness, lack of preparation and VAR are probably all factors.

One thing is certain: it is making the Premier League no less interesting...