As with virtually any early use of VARs, there are bound to be criticisms. While officials have vowed to minimize the disruption while observers check an incident, there's no shortage of people arguing that any use of VARs slows down matches by an unacceptable level. Also, they tend to operate out of central hubs, such as the Moscow hub that will be used for the 2018 World Cup. There are concerns this could lead to overseers exerting undue influence over decisions across multiple matches, such as the alleged manipulation of VAR calls in Germany's Bundesliga. And of course, VARs only come out for glaring errors or serious missed incidents. If a player takes a dive, only the ref will be involved in the call.
The World Cup implementation could have a significant effect on soccer (aka football) matches around the world. Leagues governed by FIFA aren't required to use VARs at this stage, but they may be more likely to adopt the tech if they see it in action... especially if it keeps their national team in the running.