He was the father of former West Ham United and Stoke City player Kevin Keen.
Keen started his career at Queens Park Rangers, making his debut in 1959 against York City.
Keen was the captain of the QPR side that won the League Cup and Third Division title in 1966–67.
He later moved into full-time management with Northampton Town, between 1978 and 1979, followed by his hometown club, Wycombe Wanderers, between January 1980 and 1984, leading them to the semi-final of the FA Trophy in 1981–82, then to the Isthmian League title in 1982–83.
Mike supplied a great many local youth football teams with their playing kit throughout the 1980s and 1990s.