T-SQL Query Question

I have this query:

SELECT p.PLAYER_ID , p.FIRST_NAME, p.LAST_NAME,
(
	SELECT SUM(w.NUMBER_OF_PLAYERS)
	FROM tbl_WEEK w INNER JOIN xref_PLAYER_WEEK x ON x.WEEK_ID = w.WEEK_ID
	WHERE x.PLAYER_ID = p.PLAYER_ID
	 AND w.SEASON_ID = @SEASON_ID
) AS AVAILABLE_POINTS
FROM tbl_PLAYER p

Select allOpen in new window

Basically, it gets players in a league and sums up the number of players there were each week. As you can see, tbl_WEEK has a column called "NUMBER_OF_PLAYERS".

However, a new rule has been implemented that I need to figure out how to include in the query.

A new column in tbl_WEEK has been added called "HAS_GHOST_PLAYER".

If this new column is "TRUE", then i need to subtract one from NUMBER_OF_PLAYERS. If it's "FALSE", then the query stays as-is.

I tried doing a CASE on the nested SELECT statement, which works great if there's only one WEEK in the season. But if there are multiple weeks, I get the "subquery returns multiple columns" errors.

Any help on how to go about this would be greatly appreciated.