This feature is available by pressing the "Average stats" button,

or by selecting the "Average stats" item in the "Select" menu, or by pressing Ctrl+A.

After that you will see the average teams stats window:

Here you can see the average number of goals for, against and totals for the teams of the selected championship. By default you see whole current season games stats, but you can easily set, f.e., date period by selecting "Period" Radio Button.