What week was the opponent the San Diego Chargers?
CREATE TABLE table_78821 (
    "Week" real,
    "Date" text,
    "Opponent" text,
    "Result" text,
    "Kickoff Time" text,
    "Attendance" text
)
SELECT AVG("Week") FROM table_78821 WHERE "Opponent" = 'san diego chargers'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What week was the opponent the San Diego Chargers? ### Input: CREATE TABLE table_78821 (
    "Week" real,
    "Date" text,
    "Opponent" text,
    "Result" text,
    "Kickoff Time" text,
    "Attendance" text
) ### Response: SELECT AVG("Week") FROM table_78821 WHERE "Opponent" = 'san diego chargers'