"Emotionally, it's difficult, because you don't know what to do, you're so conditioned by years of football," he said after Chile's 2-0 victory over Cameroon in the Confederations Cup. "The ball goes in, you look to the linesman and if the flag is down, you rejoice. Now, you're not sure. When can you celebrate?"

"Still, we need to remember that this is a trial," he added. "It's an experiment. And, if in the long term it brings what it is supposed to bring -- more justice to the game -- then we'll get used to it."

The early implantation of VAR has something Emmenthaler-ish about it: you can look at the holes or you can look at the cheese. Through Wednesday morning, we had five instances where it has been used and nobody can dispute that they were all correct in terms of outcome, though perhaps less so in terms of form.

So far, so good, but the biggest challenge lies ahead.

When it comes to VAR, FIFA's philosophy makes a distinction between "subjective" and "objective" decisions. The four offside calls handled by the VAR thus far were all "objective". There's not much to argue about there. We need to get used to it.

Just as you can't be a little bit pregnant, there's no more being a "little bit offside". FIFA are confident the camera angles are such that they can get this decision 100 percent right every time. Incidentally, there's a side effect to this. Linesmen have been instructed to be a lot more cautious in flagging for offside. Expect the flag to go up only in obvious circumstances. Nobody wants to be the guy who incorrectly flags when a player is through on goal, because that is the one mistake that can't be reversed. In time, you hope, assistant referees will get the hang of it. But it is something to be monitored. Having a guy on the shoulder who continually strays offside but doesn't get flagged until the VAR has a look could turn into the ultimate time-wasting exercise.

Where we may run into issues, FIFA officials concede, is with "subjective" calls -- fouls and handballs -- in the "match-changing" situations for which VAR can be used: goals, awarding of penalties and direct red cards. The protocol says that VAR can step in for "missed serious incidents" (like a player head-butting an opponent behind the referee's back, which the officials can't see because he doesn't have eyes on the back of his head) and for "clear errors".

And here things get fuzzy.

Ultimately, we're dealing with interpretation. It's not just that one official might judge the exact same incident differently than another (remember, there's an elite ref in the VAR booth). Rather, it's that the VAR, having watched four different replay angles might well reach a different conclusion because one specific angle might show something the referee on the pitch simply could not have seen. At that stage -- as with all VAR decisions where the call on the pitch is overturned -- the referee wanders over to the iPad and has the final say. But will he still consider it a "clear error" when he knows he was perfectly positioned and simply could not have seen that particular angle?

Match officials will need to wrap their heads around this. Just wait until we have the first case of a VAR overturning a "subjective" call on the pitch and the referee disagreeing. The definition of "clear error" will inevitably become a talking point. If VAR is to work long term, they'll need to get used to it and so will we.

Just as we'll need to get used to the fact that decisions will take time. VAR proponents fed us that "it will only take a few seconds" nonsense and too many fell for it. It took them nearly two minutes to green-light Cedric's goal for Portugal against Mexico. It took VAR 68 seconds to disallow Eduardo Vargas' goal against Cameroon, but if you were there, it felt a lot longer than that.

Part of the problem is that you're not sure what's going on until the referee draws his imaginary TV in the air. One thing FIFA might want to consider is allowing viewers to see what exactly the VARs are looking at. That will at least give us something to look at other than players looking confused.

Opponents will say that the game will be "slowed down". They're right. The question though is by how much and how much are we willing to tolerate? Until we actually finish the trials and get a sense of how much time is actually lost on average to VAR review and how many incidents, on average, there might be in a game it's all just hot air and blather.

Proponents of VAR talk about getting more "justice", about getting more of the big game-changing decisions correct. It won't be perfect, but it will mean fewer crass errors. "Justice", however, comes at a price.

And the truth is that we won't know whether it's worth paying until this trial is over.