user: Question: What is the league of the Third baseman player before 1973?
Columns: ['Year', 'Player', 'Team', 'League', 'Position']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1971.0, 'Willie Mays Category:Articles with hCards †', 'San Francisco Giants', 'National', 'Outfielder']
SQL:

assistant: SELECT "League" FROM "Table" WHERE "Year" < 1973.0 AND "Position" = 'Third baseman';