He played professionally in the NFL for the Chicago Bears and Dallas Cowboys, and in the AFL for the Boston Patriots and Oakland Raiders.
He played in the freshman team, before leaving school to join the Navy during the Korean War.
[3] Head coach Forest Evashevski allowed his release with a year of eligibility still remaining, in order for him to join the Chicago Bears in the National Football League.
Klein was selected by the Chicago Bears in the 29th round (347th overall) of the 1955 NFL draft, after his original class had graduated, although his college eligibility wasn't completed.
On October 4, 1961, he was signed as a free agent by the Boston Patriots of the American Football League.