user: Question: What is Opponent In The Final, when Date is before 1991, and when Outcome is "Runner-up"?
Columns: ['Outcome', 'Date', 'Championship', 'Surface', 'Opponent in the final', 'Score in the final']
Types: ['text', 'real', 'text', 'text', 'text', 'text']
Sample row: ['Runner-up', 1989.0, 'Madrid , Spain', 'Clay', 'Martín Jaite', '3–6, 2–6']
SQL:

assistant: SELECT "Opponent in the final" FROM "Table" WHERE "Date" < 1991.0 AND "Outcome" = 'Runner-up';