Chelsea boss Mauricio Pochettino says VAR is changing the approach of top-flight players.
Pochettino says a lot of the aggression in the game is waning.
He explained: "Football has changed a lot from my period. It was different. There wasn't VAR. We competed in a different way. Today, it makes you compete in a different way.
"Before, if I punch or kick someone when the ball was over there, if the referee didn't see me... there wasn't a VAR.
"Now, if the ball is over there and I kick someone or punch someone there are 200 cameras watching everything. And boom! Red card.
"And... you cannot behave like this in training. You cannot show this type of aggression. That is why players are different now. I think that is a big worry. It is tough."