18. Billy Sims:
A workhorse from Oklahoma, Sims showed tremendous promise in the early days of his NFL career. Drafted by Detroit, he became the 1980 Offensive NFL Rookie of the Year. Sims made Second-team All-Pro that year and First-team All-Pro the following year in 1981. He made three straight Pro Bowls from 1980-1982.
The future was extremely bright for the talented back. Halfway through the 1984 season, however, Sims’ career was cut short when a devastating knee injury forced him into early retirement. He spent two years trying to rehabilitate the knee but eventually stepped down. Sims tried a comeback in 1989, yet it never materialized. He truly could have been one of the greats. Instead, injury limited him to only five seasons.