Trying to calculate the average points of a user

My objective is to get as an average of each users points and display the 5 users with the lowest average in a block, and I assume using the "Math expression" in views is the way to go with this.

So what I am looking for is help with the math expression

The block I need.
user 21 - 4.7 average points
user 27 - 7.2 average points
user 12 - 9.4 average points
user 16 - 9.8 average points
user 56 - 9.9 average points
ech...

So if a user get's 1 point, then 3 points, the average would be 2 points, and that's what I want to display.

(WHAT I NEED IT FOR, YOU CAN SKIP THIS)
I have a poker club and we play a poker tournament each week. And each week players / users are "punished" with an amount of points, equal to the position the finish the tournement on. So the winner get's 1 point and the 2nd place get's 2 points and the 20th place get's 20 points and so on. The objective then is to get the lowest average when the year is done.

Right now I use excel for this, but I would really love to be able to enter the users points in the user points admin interface each week, and always have the 5 players / users with the lowest average display in a block.