user: Question: Who was the opponent at Memorial Stadium?
Columns: ['Week', 'Date', 'Opponent', 'Result', 'Venue', 'Attendance']
Types: ['real', 'text', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'September 17, 1961', 'Detroit Lions', 'L 17-13', 'Milwaukee County Stadium', 44307.0]
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Venue" = 'Memorial Stadium';