How the game calculates a result

The game works out the result of the match as soon as you hit 'got to match' right?

Surely every match should play out in the same way in the first 45mins if no changes are made at all (i.e. Instructions, tactics, subs, etc).

Why doesn't this happen? What other random factors does the game look at when calculating the outcome (i.e. a slip, an injury, the keeper spazzing out)?

The game works out the result of the match as soon as you hit 'got to match' right?

Surely every match should play out in the same way in the first 45mins if no changes are made at all (i.e. Instructions, tactics, subs, etc).

Why doesn't this happen? What other random factors does the game look at when calculating the outcome (i.e. a slip, an injury, the keeper spazzing out)?

As soon as the kickoff is made every match is different - What does the player receiving the ball do?

A) Pass to a MC

B) Pass to a DC

C) Pass to the DR

D) Pass to the DL

E) Hold the ball

F) Through ball to a winger

G) Launch the ball forward

etc

etc

What happens next? how many other decisions are taken in one half?

Its easy to see why a replayed match is never the same.

Without looking at the source code there's no way to know exactly what's calculated or how it's calculated. But for sure every one of these calculations (formulas) has a weighted randomization component that makes sure the "normal" outcome occurs most of the time.