user: Question: What was the average capacity for Vélez Sársfield?
Columns: ['Stadium', 'Capacity', 'City', 'Province', 'Home team(s)']
Types: ['text', 'real', 'text', 'text', 'text']
Sample row: ['Monumental Antonio V. Liberti', 67664.0, 'Buenos Aires', '( autonomous city )', 'River Plate and Argentina']
SQL:

assistant: SELECT AVG("Capacity") FROM "Table" WHERE "Home team(s)" = 'Vélez Sársfield';