Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_78 ( year INTEGER, regular_season VARCHAR, playoffs VARCHAR, open_cup VARCHAR )

### Question ###
What was the average year that the Nashville Metros did not qualify for the Playoffs, did not qualify for the Open Cup, and had the Regular Season 7th, Southeast?

### Accurate SQL ###

SELECT AVG(year) FROM table_name_78 WHERE playoffs = "did not qualify" AND open_cup = "did not qualify" AND regular_season = "7th, southeast"