CREATE TABLE table_72331 ("Club" TEXT, "Played" TEXT, "Won" TEXT, "Drawn" TEXT, "Lost" TEXT, "Points for" TEXT, "Points against" TEXT, "Tries for" TEXT, "Tries against" TEXT, "Try bonus" TEXT, "Losing bonus" TEXT, "Points" TEXT)

Name the points against for 51 points
SELECT "Points against" FROM table_72331 WHERE "Points" = '51'
SELECT "Points against" FROM "table_72331" WHERE "Points" = '51'