• Chairman of referees says action taken after early incidents • Total of 14 decisions overturned thanks to video in group stage

Pierluigi Collina has confirmed Fifa cracked down on holding by defenders at set pieces after a series of early incidents at Russia 2018.

Speaking to reporters at a briefing on video assistant referees in Moscow on Friday, the chairman of the referees’ committee was asked why England’s Harry Kane and Serbia’s Aleksandar Mitrovic were not given penalties for being held during games against Tunisia and Switzerland, respectively.

Collina said he would not comment on specific incidents but added: “You might have appreciated there were some incidents that suddenly disappeared or started to be punished. It’s impossible to be right from the start but because we noticed, we intervened and we fine-tuned. Things have changed during the tournament.”

In general, Collina and his committee colleagues said they believe VAR has been a huge success. Having reviewed the 48 group games, Collina said there have been 335 incidents checked – nearly seven per game – with 14 on-field reviews made by referees and three reviews made by the VAR team on “factual decisions”, such as offsides.

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Of these incidents, referees called 95% of them correctly without VAR but replays improved this to 99.3% by correcting 14 of them: six penalties awarded after an on-field review, a penalty given by the VAR because it was shown the foul occurred in the box, two penalties cancelled after on-field reviews, two potential red cards confirmed as yellows, two goals awarded after potential offsides and a mistaken identity for a booking.

“We have always said VAR doesn’t mean perfection – there could still be the wrong interpretation or a mistake – but I think you would agree 99.3% is very close to perfection,” said Collina.

There were just under 27 fouls and about three and a half cautions per game, which is consistent with the major leagues, but there has been a big increase in the number of penalties: 24 already here, compared to 10 at this stage in Brazil and South Africa. Of the 14 additional penalties in Russia, seven have come as a result of VAR.

Fifa’s big VAR-related fear was clearly that it would cause delays but the ball has been in play for an average of nearly 57 minutes at Russia 2018, up from 55 minutes in Brazil, and VAR reviews have taken an average of only 80 seconds.