2. Billy Sims
Sims came to the Lions as a much-ballyhooed prospect, the first overall pick in 1980 with a Heisman Trophy (1978) on his college resume at Oklahoma. Right out of the gate, he did not disappoint.
Sims topped 200 total yards with three rushing touchdowns in his NFL debut. That set the tone for a big first season (1,313 rushing yards, a league-high 13 touchdowns; 51 receptions for 621 yards and three more touchdowns) as he (naturally) won Offensive Rookie of the Year and earned a Pro Bowl selection.
Sims had quite the encore in 1981, with 1,437 rushing yards and another 13 scores on the ground.
Sims played just nine games in 1982, but he still led the league with 206 touches and he earned a third straight Pro Bowl selection. He topped 1,000 yards on the ground again in 1983, while nearing 1,500 yards from scrimmage. A major right knee injury during the 1984 season wound up ending his career, after two years spent rehabbing before he gave up the effort and retired. A comeback attempt for the 1989 season never really got any serious traction with the Lions' brass at the time.
There's naturally a lot of "what might have been" with Sims' short career, and perhaps with modern medicine it wouldn't have had to end as quickly as it did. But the original No. 20 among Lions' great running backs belongs at No. 2 on this list.