user: Question: Which surface has an Opponent of Fernando Verdasco?
Columns: ['Outcome', 'Date', 'Surface', 'Opponent', 'Score']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Winner', '14 April 2008', 'Clay', 'James Blake', '6–4, 1–6, 7–5']
SQL:

assistant: SELECT "Surface" FROM "Table" WHERE "Opponent" = 'Fernando Verdasco';