His league debut came in February 1939 , in a 4 -- 1 win over Leeds United .
Mullen joined the Midlanders in June 1937 , turned professional on his 17th birthday , and remained with the club until his retirement in May 1960 .
Mullen 's league debut came in February 1939 , in a 4 -- 1 win over Leeds United .
Mullen joined the Midlanders in June 1937 , turned professional on his 17th birthday , and remained with the club until his retirement in May 1960 .