First of all - I think You talk about Game Shape, because it depends of minutes per week. Meanwhile weekly changes of stamina are very little.
Comparition to NBA has no sense. This game is designed in this way that we can play without log every day. More matches would be too many for most of users and I suppose number of users would be decrease very quickly.
So we have 3 matches per week and it's good. And practically it doesn't matter because if we had for example 6 matches per week the same problem would appear, only number of minutes would be different (twice more than now).
Managment of minutes makes game is more interesting so if this factor is be deleted, then game will be worse. And the most important thing - every user has the same problem so chances are equal for everybody. And winner is who is able to solve this problem better in his club.