Mostly you can notice the match is fixed if the player is intentionally not doing its role like in basketball they miss the shot, in boxing they miss the punch or too slow, in a horse race, the rider makes the horse not conditionally well prepared, and more, of course, you are a fan of the game you want to bet and there are a lot of people who wants their player wins and there's a possible under the table transactions that might affect also the other bettors, but of course if you don't have a power too you cant do anything about match fixings.
I agree if you are keen on details and you know players and participants and their statistics and have seen them play many times you expect the same performance in every game, but if you see something like intentionally missing the shot and intentionally making mistakes then there's something wrong if a player is having a bad night the coaching staff will replace him but if they insist that he stay on the court, then there's a possibility that even the staff is participating in fixing the game.
I have read several stories in basketball. You can easily spot the game fixing if you are very familiar with the members of the team.
Because you will know if they are not in their normal performance and just throwing the game.
Usually, it is because of the big bets involved. When it comes to boxing, you can also see it how the boxer is doing his punches inside the ring.
If you are an enthusiast of a particular sports, spotting the unusual movements of their players would be easy.
