CREATE TABLE table_name_52 (goals INTEGER, position VARCHAR(255), first_appearance VARCHAR(255), last_appearance VARCHAR(255), appearances VARCHAR(255))
What is the average goals when the last appearance was before 1984, there were more than 17 appearances, the first appearance was before 1961 and the position was mf?
    
SQL: SELECT AVG(goals) FROM table_name_52 WHERE last_appearance < 1984 AND appearances > 17 AND first_appearance < 1961 AND position = "mf"