I feel that a lot of people say that a team got lucky when the opposite side has a lot of chances but misses them, or when their goalkeeper stops a lot of shots.

I disagree. Saying that would mean that all the keepers are the same and that stoping a shot is just luck. Or that not being clinical in front of goal is just unlucky. those are skills that you train for. Hitting the bar is not bad luck, its frustrating yes, and its very close to a goal, but in the end its just an shot out of target.

I'm obviously bringing this up because of the PSG-Napoli game, but I have seen this for many other games. Specially for the keeper thing. So lets not make this about this specifique game :)

For me luck in football is when the ref favours a team (hopefully unwillingly) and makes a lot of mistakes. I would perhaps also consider luck a deflexion, and even that i'm not sure about.

What do you think?

A deflexion that goes into goal, especially if the keeper was moving to stop ball on its initial path, is pretty lucky.

Player still being on the field despite making a high number of nasty fault that could have deserved a red or 2 yellow is lucky.

Own goal depending on the situation can be lucky.

Player making poor decision, which gift opponent goal is lucky for the opponent (think Karius against Benzema or Loris in the world cup final).

As for player creating lots of chance and not scoring, it can be a bit unlucky for different reason but at the end of the day, I think you are right, its mostly on the attacking team not being clinical enough.

Same goes for keeper, they are rarely any luck involved in their save, its mostly skill, exception would be when the ball hit the bar and goes straight into their hand instead of into an attacker path or inside the goal, thats what I would call lucky.

On my last two point though, having a lots of shots in a game doesn't alway mean your team was good, if most of those shot were long range and not that dangerous, then despite boosting the stat, its doesn't reallly matter how many shot there is.

The team that creates the highest number of high quality chances wins 95% of the time. The other 5% are deflections, weirdness, and things known in the video game community as "FIFA AIDS."

They have an element of luck, but a team still makes their own luck. A deflected shot that turns into a goal needed the team in a position to take a shot where a deflection could occur. Hitting the post from the perspective of a shot is the same result as missing the net. It is possible to quantify this stuff.

Highest number of high quality chances, where high quality are the key words. Because lets not lie, if you shoot 100 times but 95 of those aren't even on target, its pretty much the same as having only five shot but on target. Whats more, a shot on target straight on the keeper is a lot different than a shot on target when the goalkeeper isn't even in his box. You get what I mean, different situation can alter how important stat seem to be.