Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_14 (capacity INTEGER, stadium VARCHAR, current_manager VARCHAR)

### Question ###
What is the capacity for the stadium of kadrioru stadium and a current manager of sergei ratnikov?

### Accurate SQL ###

SELECT AVG(capacity) FROM table_name_14 WHERE stadium = "kadrioru stadium" AND current_manager = "sergei ratnikov"