Sunseri attended the University of Pittsburgh, where he played for the Pittsburgh Panthers football team from 1978 to 1981. After beginning his career as a walk-on, Sunseri was a three-year starter and anchored a defense that led the NCAA in total defense in both 1980 and 1981. During his senior year, he was named a team captain and a consensus first-team All-American.
After graduating he was selected by the Pittsburgh Steelers in the 1982 NFL Draft; however, he suffered a career ending knee injury during training camp and was given an injury settlement and released from the team.
Between 1985 and 1992, Sunseri worked as a defensive line and linebacker's coach for his alma mater, the University of Pittsburgh. After Paul Hackett was fired as the team's head coach during Pittsburgh's 1992 season, Sunseri was promoted as an interim head coach for the final game versus Hawaiʻi—a 36–23 loss for the Panthers.