Table: seattle_sounders_stats
Columns: year
league
reg_season
playoffs
us_open_cup
avg_attendance

Question: What was the regular season standings for the year when the playoffs reached the conference semifinals and the team did not qualify for the US Open Cup?
SQL: SELECT "reg_season" FROM seattle_sounders_stats WHERE "playoffs" = 'Conference Semifinals' AND "us_open_cup" = 'Did not qualify'