The issue isn't not being able to protect the fracture.
The issue is being able to protect the fracture without covering it in a substance that might cause injury to an opposition player.
I remember Gary Lineker wearing a ligh-weight cast in the World Cup in..... (Spain), (somewhere anywhere), and there was a big deal anout whether it would be allowed with regards to the damage it might do if it caught someone across the face for examnple.
I've got a feeling that his cast was made of foam in the end and not the hard substance that we would expect.
As for playing with a broken wrist, it's not the same in every case as there are many small bones in the wrist area that might gat cracked but which wouldn't be as big a deal as some other bones in the same area.
I never broke my wrist, but broke my scafoid, (bone behind thumb), playing rugby and just got on with it.
I also broke bones in my right hand, (bones behind the fingers), 3 times in 1 season and never missed a game. It maybe wasn't the smartest move in the World but back in those days you just popped a couple(ish) of pills before each training session/match to allow you to do the contact and paid the price afterwards.
God that was a hard season

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