user: Question: On what year did Newcombe first face Clark Graebner in a final match?
Columns: ['Outcome', 'Year', 'Championship', 'Surface', 'Opponent in the final', 'Score in the final']
Types: ['text', 'real', 'text', 'text', 'text', 'text']
Sample row: ['Runner-up', 1966.0, 'U.S. Championships (1/1)', 'Grass', 'Fred Stolle', '6–4, 10–12, 3–6, 4–6']
SQL:

assistant: SELECT MIN("Year") FROM "Table" WHERE "Opponent in the final" = 'Clark Graebner';