Career
He played as a defender and made 400 Football League appearances in the 1960s and 1970s with Birmingham City, Nottingham Forest and Derby County. After his playing career, he managed a number of clubs, including Tulsa Roughnecks of the North American Soccer League, whom he led to the league championship in 1983. In November 1965, he was transferred to Nottingham Forest and became their captain.
He transferred from Forest to Derby County in February 1970 for a fee of £100,000.
His role on the field varied. During his career Hennessey accumulated a total of 400 league appearances, as well as being capped by Wales on 39 occasions.
Hennessey was forced to retire at the end of the 1972-1973 campaign and initially went into coaching. After taking a position (for the second time) as an assistant coach of Tulsa Roughnecks in 1980, he took over as manager mid-season in 1981, replacing Charlie Mitchell.
In 1983 Hennessey led Tulsa to the NASL championship, winning Soccer Bowl "83 by a 2–0 score over Toronto Blizzard.
However, the team"s financial instability led him to resign after the season.