Great question! This can be achieved a number of ways. In order to display “empty” cells in your repeating group you’ll need to set the data source of the RG to a data source that has the number of items you need to display the correct number of cells.
Since you need relatively few items for this list a potential solution here would be to create an option set with 15 dummy values. There are also a number of plugins that allow you to generate temporary lists.
You’ll then need another repeating group to store the actual player data and in your original RG you can pull the appropriate player data to each cell with an expression like “Player data RG’s list of players: item # current cell’s index”(Or a more sophisticated search if necessary). This should allow you to display empty cells when there is no player data and populated cells where there is player data.
Hope this helps!