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_39 ( round INTEGER, position VARCHAR, pick__number VARCHAR )

### Question ###
What is the mean round number for center position when the pick number is less than 23?

### Accurate SQL ###

SELECT AVG(round) FROM table_name_39 WHERE position = "center" AND pick__number < 23