Players are Predictable
Every player has a repertoire of skills, knowledge, techniques and habits ( we'll call them "things they do") that they bring to every match.
If we apply what they call 80/20 thinking to analysing this player, it should follow that they will use 20% of these "things they do", 80% of the time
If you figure out what the 20% of "things they do" are, the player you are up against suddenly becomes very predictable.
To put it in context, if a full forward you are marking wins the ball, there are probably 10 things they could do, but there are 2 things they generally do, and probably will do.