user: Question: What Opponent played on the Date May 21?
Columns: ['Date', 'Opponent', 'Score', 'Loss', 'Save']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['May 1', 'Giants', '4 - 3', 'Garrelts (0-1)', '|| 14,490 ||13-6||']
SQL:

assistant: SELECT "Opponent" FROM "Table" WHERE "Date" = 'May 21';