What you're trying to say is that:
a. A defender sticking out a leg is a function of defending not luck
b. All shots towards goal are lucky: ones go into the net and luckily they don't hit anyone, ones they hit someone and luckily go into the net.
You talk about everything being physics, well it's not. Physics like circular acceleration, wind speed, force that the ball was hit with, place where the ball was hit will determine the trajectory of a ball.
The trajectory of a ball can be positive(in the net) or negative(random position). Based on that you're arguing that everything is down to physics but it's not.
The changes of the ball's trajectory are a result of a physics process, the same with the final destination. Factors that can determine the trajectory of a ball can also be based on luck, even if the process of trajectory change is pure physics. In basic simple English, any change suffered by the ball on the field is a result of a pure physics process, but the existence of other factors that create the trajectory change can be also put down to luck/coincidence. That's the part you don't really get. (the ball hitting a pigeon and going into the net is a results of a physics process, but the presence of the pigeon is a consequence of reality, not 100% down to physics).
