(Reuters) - Major League Soccer will embark on a new era this weekend with the introduction of a video review system - Video Assistant Refereeing (VAR) - across all matches.
The technology will be limited to four potentially game-changing situations: helping referees reduce errors near goals, penalty decisions, red cards and cases of mistaken identity.
It has already met with mixed reactions from players and coaches.
"I'm looking forward to it because just from an idea, philosophy standpoint, it will .... get correct calls and that's what we want," Portland Timbers coach Caleb Porter told The Oregonian newspaper.
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"There's a lot of calls this year that if we had VAR, it would have changed the game for us, meant more points for us, maybe a few where it would have meant less too. But I think at the end of the day, it will improve key decisions that I think get missed quite a bit in this league."
The new system, which has been three years in the developing, means that starting with this weekend's 22 games, there will be a fifth member of every officiating crew in a booth in the stadium with access to all broadcast replays.
If a VAR notices a potential clear error or missed incident, this official can notify the head referee, who will then decide whether to conduct a video review.
Not everyone welcomes the innovation, however.
"I don't like it," Toronto FC midfielder Michael Bradley told the Toronto Sun. "I'm a traditionalist when it comes to this stuff. I think the human error, when it comes to refereeing, is part of it."
MLS is one of the few leagues around the world that will formally integrate video review during live competition this year but more could soon follow.
The International Football Association Board, the world governing body which oversees the rules of the sport, is expected to make a final decision in 2018 or 2019.
"It's not going to change the way the game is played," Howard Webb, a former World Cup and Premier League referee who is now the face of VAR, told The Atlanta Journal-Constitution.
"If it does that, it's not doing the job it's meant to do. The game is beautiful. We love it for what it is."
(Reporting by Frank Pingue in Toronto; editing by Julian Shea/Jeremy Gaunt)