With fans and other leagues watching, Major League Soccer has introduced video replay in dramatic style.

The Video Assistant Referee, or VAR for short, ruled out a goal in FC Dallas' first-ever loss to the Philadelphia Union on Saturday.

The VAR disallowed Maximiliano Urruti's late goal for Dallas after video evidence showed that forward Cristian Colman fouled Union goalkeeper John McCarthy before the shot and he wasn't able to get to the ball. Philadelphia won 3-1.

The decision took about two minutes.

The VAR also had an impact on Sunday's game between the Portland Timbers and the LA Galaxy when Gyasi Zardes' apparent go-ahead goal in the 11th minute was disallowed because of a handball.

The goal would have given the Galaxy the lead and arguably could have swayed the momentum to Los Angeles. Instead, the Timbers went on to win 3-1.

"I think everyone has their opinion on it," said Portland defender Liam Ridgewell. "But, obviously, it's coming into the game and it worked in our favour. Ask me next time when it doesn't. It was great today. So we'll wait and see next time."

The goals in Portland and Philadelphia were the only two that activated video review.

"I saw it after the game and still I have to say that it generates a lot of thoughts, but we respect it," Dallas coach Oscar Pareja told reporters. "I have to be honest and say if the referee had the chance to review it, the (Video Assistant Referee), they made the decision, I have to assume that it is correct."

There are many eyes on MLS's rollout of the VAR, who serves as the fifth member of the officiating crew at any given game.

The VAR at each MLS stadium monitors all video feeds of the game that are available, focusing on "potential clear and obvious errors or serious missed incidents" involving goals, penalty kicks, straight red cards and mistaken identity.

If a review is required, the VAR will alert the referee on the field, who will make a box gesture with his hands to indicate the VAR is examining a possible error. All final calls will lie with the head referee.

Two other top-tier leagues will add a VAR soon. The German Bundesliga will debut video replay for the season opener between Bayern Munich and Bayer Leverkusen on Aug. 18. The Italian Serie A will also introduce its version after adding goal-line technology last season.

Video replay is currently being tested on the international level, used in the Under-20 World Cup and the Confederations Cup in Russia. FIFA, soccer's governing body, plans to use it at the 2018 World Cup.

Soccer's adoption of the technology is not without its detractors, some who worry it will have unintended consequences — like making games longer.

Greg Gordon, a Glasgow-based soccer scout and longtime journalist who writes for the website howtowatchfootball .co.uk, is one of those closely watching how MLS applies video replay after seeing some of the controversy caused by its use on the international level.

"The beauty of football — unlike maybe some American sports, which I also love — is that there's a constant ebb and flow to the game," he said. "And actually the use of video refereeing, as we've already seen in a few instances, can really lead to the breakup of the speed of the game. But it also can really lead to what you could call catastrophic moments of just mass confusion."

And indeed, there seemed to be some confusion among those watching MLS games this weekend about when it could be used, or whether it should be used.

In Portland, where supporters are known for their chants and songs throughout matches, fans chanted "V-A-R" after what they saw as a foul on forward Fanendo Adi by Galaxy defender Dave Romney.

Galaxy goalkeeper Brian Rowe said after Sunday's game that he's taking a wait-and-see approach .

"I haven't seen a replay yet (of the disallowed goal). But I think it's something, VAR getting introduced, it's something that is going to change the flow of the game a little bit. So it's something that we're going to have to get used to as players. You get that energy of, 'OK, We got our second goal we, we're going to go up, OK we've gotta defend now.' Then all of the sudden it's, 'Wait a couple of minutes,' and it gets called back and you're in a different kind of mindset and it's tied again," Rowe said.

"It just adds an extra layer to it and it's something that as players, it's the law now so we've just got to get used to it."