After four years in the U.S. Army during World War II, Allen was drafted in 1947 by the Chicago Cardinals of the National Football League (NFL).

He instead went to play for the Cleveland Browns of the competing All-America Football Conference, who won the league championship that year.

Allen played in Cleveland for one season, returning to the University of Kentucky in 1948 to serve as an assistant football coach under Bear Bryant.

He stayed at Kentucky after Blanton Collier took over as head coach in 1954, working as the team's defensive coordinator.

[1] He played varsity basketball between 1940 and 1942, earning a spot on the Southeastern Conference all-star team in his final year.

[8] Allen had four completions in limited playing time for Cleveland as the team finished the season with the 12–1–1 record and beat the New York Yankees in the championship game.

[1] Allen remained an avid golfer as he continued his coaching career, winning the Kentucky Amateur Golf Championship in 1955 and 1958.

[1] "He was a tremendous coach, as well as a real bright type of guy who had a statistical mind," Landry said after his death.

[1] Eugene Meeks, who played college football with Allen, said he was one of Kentucky's best-ever athletes and a dominant golf player during his time at the university.