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_15 (play_offs INTEGER, total VARCHAR, league VARCHAR, player VARCHAR)

### Question ###
What is the mean number of play-offs when the league number was bigger than 18, where the player was John Grant and the total number was bigger than 25?

### Accurate SQL ###

SELECT AVG(play_offs) FROM table_name_15 WHERE league > 18 AND player = "john grant" AND total > 25