After Arsenal’s disappointing start to their Champions League campaign, one thing stood out for me.

It wasn’t the performance, it wasn’t the goals, it wasn’t even the result. All of those can be rationally explained and countered, but it was the reaction afterwards that was surprising.

The game in Zagreb was a perfect example of how you only need a tiny amount of details to go against you for you to lose a game, and that the list of details that could possibly go against you is as long as the distance between the pitch and the stands in Zagreb. (At one stage of the game, I wouldn’t have complained if the ball boys needed a taxi to go fetch a clearance, they were so far away from the players.)

For example; all the scouting, all the tactical briefings and all the opposition research can be rendered null and void by a referee who just doesn’t like the look of you. We’ve all played in games that were officiated by someone, who no matter how nice or polite or well-mannered you are, is going to single you out because they don’t like you. Why they don’t like you is irrelevant, and any enquiries as to why you’ve been treated like this usually only makes things worse.

That’s why I don’t want to criticise Olivier Giroud too much for getting sent off. Yes, it was rather silly to give the referee an excuse to send him off for a second booking by lazily sticking out a leg as a tackle, but it would only have been his first booking if the referee hadn’t given a very soft foul against Giroud 15 minutes previously. It was such a bad decision, you can’t blame Giroud for reacting as he did.

Then there were the goals themselves. If Giroud’s header loops two inches to the left, it goes in off the post and not bounce into the air. If that same header loops two inches to the right, the ball bounces away from the keeper instead of landing directly at his feet and Giroud has a tap-in. Dinamo’s first goal wouldn’t have been a goal if David Ospina deflects the initial shot two inches either side of Alex Oxlade-Chamberlain. Sometimes the luck is with you and sometimes it isn’t, and in Zagreb, Arsenal were unlucky on both occasions.

Then there was the team selection. Before the game, everyone was saying this was a good opportunity for Arsene Wenger to rotate the squad a bit, give a couple of key players a rest and hand a chance to a couple of squad players to prove that they should be in the first team more often. After the game, everyone was saying that Wenger should have played his best 11 players. Why? Because we lost?

Judging decisions purely by the result is always a bad way to determine how good the decision actually was. If Arsenal had won that game, we’d be praising the depth of the squad and Wenger’s willingness to make changes in order to keep players fit. If Francis Coquelin had started the game and got injured, then we’d be slating Wenger for not giving him a rest. Using information available after a decision was made to evaluate that same decision is unfair on the person who made it.

Of course, that doesn’t mean the decision to rotate players was flawless. I’d like to have seen Petr Cech’s reaction when told he wouldn’t be playing in a Champions League game, for example. Also, playing Mikel Arteta and Santi Cazorla in midfield against a team looking to counter by running through the middle was not ideal, but that was a problem caused more by not buying sufficient cover for Coquelin in the summer, than it was the decision to play Arteta.

But even with all that said, who could have predicted that Mathieu Debuchy would play like a man filled with desperation instead of an international right-back? Who foresaw that David Ospina would be possessed by the ghost of Manuel Almunia midway through the second-half? It would be pretty harsh to blame Wenger for not being able to see into the future and avoid picking either of those players in advance, no?

It doesn’t just work in a negative way either. Chelsea were desperate for a result in their first Champions League game in order to relieve some pressure off themselves, yet they started like a team devoid of confidence would. When Eden Hazard starts missing penalties, you know a team is rattled. What they needed was a bit of luck to go their way, and they got it through a fluke free-kick that opened the scoring. After that, their opponents collapsed and Chelsea won comfortably.

Arsenal didn’t get that break against Dinamo. As much as fans want to try and see patterns in past performances, sometimes a game happens where everything that can go wrong will go wrong, and there’s very little that can be done to prevent losing that game. Being frustrated that Arsenal lost a game is fine, but it’s always important to remember just how many things can go wrong in a single game, and how few of those have to happen for us to lose.

The margin for error in football is tiny, and it can be sometimes eradicated by matters completely out of our control. One of those games just occurred in Zagreb. We can only hope that another one doesn’t happen at Stamford Bridge on Saturday.