CREATE TABLE table_27454 ("Opponent" TEXT, "Played" FLOAT, "Won" FLOAT, "Lost" FLOAT, "Drew" FLOAT, "Premiership points" FLOAT, "Points for" FLOAT, "Points against" FLOAT, "Percentage  ( % ) " TEXT)

What was the minimum points against if the opponent is Port Adelaide?
SELECT MIN("Points against") FROM table_27454 WHERE "Opponent" = 'Port Adelaide'
SELECT MIN("Points against") FROM "table_27454" WHERE "Opponent" = 'Port Adelaide'