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