Allen's career started against the New York Giants, a game where Lawrence Taylor recorded eight sacks. By midseason, Allen was relegated to Special Teams. During the offseason, Allen moved to the center position.
After a subpar rookie season, Allen tested positive for cocaine after reporting to Eagles training camp in 1986. The Eagles released him in October 1986. A week after being cut, he was charged with rape and spent the next 33 months in prison. He was banned from the league for life soon afterward. Buddy Ryan thought so little of Allen that he once described him as someone who could only be useful "if you want someone to stand around and kill the grass... he looks like a USFL reject." In 2011, Deadspin ranked Allen the 4th-worst football player of all time, noting "The ninth overall pick out of Indiana had a special way of blocking opposing pass rushers. He would lean his body forward, then fall down." and "Never had the Eagles had a combination of bad person-bad player that could match this guy."