Highsmith attended Christopher Columbus High School, where he played defensive end and helped his team reach the state championship final in 1982, while receiving All-American, Florida high school Defensive Player of the Year and the Dade County Athlete of the Year honors.
He was a member of the 1983 Hurricanes squad that won the national championship, and led the team in rushing during the 31–30 victory over Nebraska in the Orange Bowl.
In 1984, Jimmy Johnson arrived as the new head coach and named him a starter as a sophomore, rushing for a team leading 906 yards on 146 carries (6.2 average) and 11 touchdowns.
In his last year, he was recognized as the nation's best fullback, while posting 442 rushing yards (led the team) on 105 carries (4.2 average) and 8 touchdowns.
In 1988, he started 16 games, rushing for 466 yards (third on the team) on 94 carries for a 5-yard average, while developing into one of the best blocking fullbacks in the NFL.
[4] Although he had started 40 straight games with the Houston Oilers, he had a series of offseason knee surgeries that had doctors recommending against the Dallas Cowboys acquiring him in 1990.
[5] Head coach Jimmy Johnson, knowing Highsmith from his playing days at the University of Miami, ignored the medical advice regarding a potentially career-ending knee condition[5] and went ahead with the proposed trade on September 3.
[6] He played in 7 games (5 starts) as the lead blocker for rookie Emmitt Smith before being placed on the injured reserve list after not being able to fully recover from his previous knee surgery.
In 2012, he accepted a senior personnel executive position in the front office of the Green Bay Packers.
[13] After consulting for the Seattle Seahawks in the 2020 offseason, he accepted a full-time position as a personnel executive with the team on June 12, 2020.