I think I see where you are going but I don't think there is a "lone winner" for a race. I believe that if you were able to repeat the race it is more than likely you would get a different winner.

For each race there are literally millions of different ways the race could be run, some result in horse A winning, some in horse B, some in Horse C, etc. When we are doing ratings we are trying to work out what the chance of a scenario where horse A winning occurs, the chance of a scenario where horse B winning occurs, etc.

If you were able to repeat the race you would get a different scenario as the chances of the race being run in EXACTLY the same way are millions to one - of course the different scenario may still give the same winner but that is where the probabilities come into it.

How many times have you watched a race and seen a runner lose the race because the jockey made the decision to try to go around the leaders but if he had waited a split second longer he would have seen the gap opening for an easy run through? Or a horse lose the race by missing the start? Or an outsider win because the leader went wide on the home bend taking 3 or 4 horses with it and giving the outsider the run through on the rail? If you repeated the race it is probable that these factors would change and therefore the race result would change.

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