Nice and easy using the index function. Index is a table calculation, so you can set how it works out the rank in different ways. In the first sheet it's Table Down. However that table is sorted (points, assists, name), index will always be 1 to 12 down). The second sheet I've set the index to sort along points (Edit table calculation, sort Points descending). You can see in the third sheet I've changed the table sort to assists, but the index rank remains on points. The only caveat to this that equal rank is not a feature (1,2,3,3,5,6,7...)
This is perfect Alex. Very easy too! I just created a calculated field with index() as the formula and dragged it onto the measure values shelf. Works like a charm!