Referee’s heart beat lower without fans

passion.’’

Aytekin said he believed the league would become increasingly competitive as the players and referees grew used to the ‘‘ghost games’’, but his comments have shone more light on the consequences of playing matches without supporters.

He added that there were situations on the pitch that ‘‘would have been more hectic’’ if fans had been in the stadium as usual, although he did not believe ‘‘the Revierderby’’, which Dortmund won 4-0, was any less intense for the players.

Keith Hackett, the former Premier League referee and ex-head of the refereeing organisation Professional

Game Match Officials Limited, told The Daily Telegraph that the lack of crowds could have an adverse effect on the quality of refereeing.

‘‘Because there is no crowd, there probably does not feel to be the same level of pressure,’’ Hackett said. ‘‘That can create a problem because the referee can have periods where he is not concentrating as much as he should do.

‘‘If the concentration is not sharp then you could miss the big decisions. In front of a crowd, there is absolutely no doubt that the adrenalin rush keeps the heart rate up and keeps you on your toes.’’