Table schema:
CREATE TABLE table_name_86 (opponent VARCHAR, result VARCHAR, week VARCHAR, attendance VARCHAR)

Question: What is the Opponent at the game with an Attendance of 64,900 in Week prior to 15 with a Result of L 38-31?
SQL: SELECT opponent FROM table_name_86 WHERE week < 15 AND attendance = "64,900" AND result = "l 38-31"