user: Question: What is the average Ends with a Since of 2003, and a Name with Márquez?
Columns: ['Nat.', 'Name', 'Since', 'Goals', 'Ends', 'Transfer fee']
Types: ['text', 'text', 'real', 'real', 'real', 'text']
Sample row: ['ESP', 'V. Valdés ( VC3 )', 1998.0, 0.0, 2010.0, 'Youth system']
SQL:

assistant: SELECT AVG("Ends") FROM "Table" WHERE "Since" = 2003.0 AND "Name" = 'Márquez';