There are so many variables involved in a single game, that you can't always draw meaningful conclusions from that game. For example, one team might in general win 90% of matchups against a certain team, but the one that actually happens in the GD season was the 10% chance, where the lesser team won. The same holds true for player performances, where players will have good games and bad games, sometimes even when it doesn't necessarily make much sense.
Over the course of a season though, performances will mostly match what is expected. The ones that don't can be chalked up to upsets, much like real life.