Manchester City's Martin Demichelis walks off after being shown the red card during their Champions League round of 16 first leg soccer match against Barcelona at the Etihad Stadium in Manchester

With another set of first leg Champions League round of 16 matches coming up, I want to talk a bit about luck. For me, the biggest problem with understanding how luck influences outcomes in football matches is the word itself. ‘Luck’, along with ‘fortune’, evokes an unexpected and inexplicable advantage. You’re late for work, you rush out the door to get to your nearby stop, and lo! The next bus arrives to pick you up right away, and even better, it’s mostly empty so you have room to take a load off. What a stroke of luck!

When an analyst refers to “luck” however, what they usually mean is random variation. Stuff happens, in other words. And so the next day you get to the bus stop bright and early, but the bus ends up being twenty minutes late and it’s so packed you have to wait for another ten. No two days will be the same, though you will roughly get to work around the same time every day.

This is the influence luck (or variance) at its most obvious. Few people have trouble understanding the concept when laid out this way. But when we talk about ‘luck’ in sports however, the conversation completely changes.

“Luck” in the colloquial sense is usually only acknowledged when John Terry slips when taking a penalty, or when Darren Bent’s shot against Liverpool deflected off a balloon giving Sunderland the lead. You can see why: sports is all about talent and intention.

Consider the Champions League. Managers foment tactics, and those tactics either succeed or fail in their objective. Teams field eleven elite players, paid enormous sums for their considerable skill. Everyone is focused on a single outcome: winning the match (or drawing it depending on the opponent and the leg). Sure, some of these people will make mistakes. But this could just as likely be the result of a lapse in concentration or confidence, or a bad decision by the manager, than anything to do with dumb luck.

And here we get into another misunderstanding about variance: that just because it appears to be random doesn’t mean that it is actually random. ‘Random’ variance is just a variable you haven’t met!

This is absolutely true. But let’s go back to our example with the late, crowded bus. Maybe the bus was late because the traffic was bad. Or maybe that stupid lazy bus driver showed up to work hungover and messed up the route schedule. Or maybe there was an accident further up the route. Or, and as is much more likely the case, the cause was abstract, the added effect of tiny variations in the speed of cars and the timing of lights and the slush on the road and the number of people waiting for their stop and the individual commuters who all decided to leave their homes at a particular time of day. If we were omnipotent beings, we could calculate all this, but we can’t. So for all intents and purposes, it is “random.”

This is what analysts tend to mean by “luck.” You can see it in any football match. The relative skill of both sides was evident, as were their weaknesses. But much of what makes these players great is adjusting to a host of changing circumstances outside their control. The Demichelis red card which led to Barcelona’s first goal against City last night in the Champions League offers a good example.

Here is the newspaper narrative, chosen from a match report at random but generally reflecting consensus:

Pellegrini’s team had generally been coping until the moment, eight minutes into the second half, when Andrés Iniesta expertly picked out Messi’s run and Demichelis, hopelessly out of position, clattered into the four-time Ballon d’Or winner with a desperate attempt to recover.

We know the rest. Demichelis was sent off, and Messi scored the resulting penalty giving Barcelona a 0-1 lead and a precious away goal. But a look at the second-by-second events leading to the penalty reveal a much more complex situation.

Iniesta has the ball at his feet with Busquets ahead of him just behind Zabaleta, Messi well ahead of the play, and Kompany a littler further inside. Demichelis is a good three metres behind Messi. What happens next is crucial. Zabaleta can’t keep up with Busquets for pace. Kompany sees that and begins moving toward his running path to prevent Iniesta from sending a through ball clear on the flank. Messi meanwhile has slowed to get onside for the pass he knows is coming and receives just as Demichelis gets near him. In fact, Demichelis is the only City player aware of what’s happening. This isn’t because he’s a genius, but because Kompany took a fifty-fifty gamble on where Iniesta’s perfect pass was heading. Meanwhile the fourth City player in that backline (Clichy?) hasn’t changed his run, perhaps accounting for the Barcelona player behind him.

So who’s at fault here? Zabaleta for not keeping pace with the outside winger? Kompany taking a gamble by covering for him? Hart for not coming further out of goal sooner? Demichelis for making a last ditch, from-behind challenge on the best striker in the world? The linesman for not calling a free kick? Hart for not saving the penalty? Or is everyone on City at fault for their positioning on the break when Barcelona was in possession? Or perhaps they’re all exonerated by the sheer brilliance of Messi’s movement and Iniesta’s perfectly weighted pass?

Isn’t it safe to say that while these events were the outcome of a set of intents, they resulted in a extremely complex, ever-changing sequence of possibilities that could not be perfectly foreseen or accounted for as they unfolded in real time?

This complexity why no two games look the same, and why any team can win on their day (it’s also why football is pretty kickass). Over time, skill becomes more important (which is why analysts love the league but stay away from the CL), but in the Champions League where ties are decided on two leg matches, players can only rely on their skill, their intelligence, their trust in their teammates and a lot of good luck. Sure, variation also affects things like the bend of the ball on a shot or a bad bounce or two. But it’s more often the complexity hidden in plain sight.