The video assistant referee system (VAR) is changing the art of defending, according to Tottenham defender Jan Vertonghen, reports BBC Sport.
Dutch referee Bjorn Kuipers awarded Manchester City a controversial penalty in Tuesday night's Champions League quarter-final first leg against Spurs.
"Football is always a very emotional game, and VAR is changing that a bit," 31-year-old Vertonghen said.
"I think we have to change the way we defend."
VAR is set to be used in the Premier League from next season and Vertonghen believes its introduction will lead to a large increase in the number of penalties awarded.
"I think so many things look like a penalty in slow motion," the Belgian defender said.
"We are not pulling people down but even a small touch, if you watch it 20 times in slow motion, it will give so many more penalties.
"I think in the next few years in the Premier League, you will see at least 20, 30, 40 more penalties.
"I think we all need to adapt. Sometimes you can't do anything else than put your body on the line. It's important that referees think as a football player sometimes.
"You can't even touch anyone. Before it was quite physical, but in a fair way, now you are too scared to get close to someone."