CREATE TABLE table_37771 ("Week" FLOAT, "Date" TEXT, "Opponent" TEXT, "Result" TEXT, "Attendance" FLOAT)

Who was the opponent during the game that had more than 31,891 people in attendance?
SELECT "Opponent" FROM table_37771 WHERE "Attendance" > '31,891'
SELECT "Opponent" FROM "table_37771" WHERE "Attendance" > '31,891'