I am working on a soccer game engine in C#, and specifically the safety of a pass along the ground. I'm having a hard time thinking of a suitable formula to indicate how far an opposing player might be from intercepting a pass. I want to be able to give a likelihood between 0 and 1, ignoring all other factors like ball height, player pace/ability/etc. In other words, I'm thinking mostly about current position of the opposing player.
What formula would you deem most appropriate? Perhaps an arc with the possession player at the centre and the recipient player on the radius?