Leonard Thompson was drafted by the Lions back in 1975 and started his career as a backup running back and wide receiver. He was seldom used in either role early on with only 31 rushes for 91 and a touchdown in 1977 being his best campaign on the ground. After that campaign, he was shifted to more of a receiver role but kept the number 39 which made him stand out at a position where everyone else had to wear a number in the 80s.
By 1979, Thompson started to find his rhythm as a route-runner and had 451 yards and two touchdowns on 24 receptions. By 1980, he was a regular starter, lining up with the first-team in 12 of 16 games. His impact was minimal in the number of catches as he had just 19 on the year. However, he averaged more than 26-yards per grab and finished with 511 yards.
Thompson never ended up being able to gain more than 773 yards in a single year but he was incredibly consistent during a stretch that covered the 1983 through 1985 seasons. During those campaigns, when he was over the age of 30, Thompson had 752 yards, 773 yards, and 736 yards while also scoring 14 touchdowns in that stretch as well.
He was never dominant but he was the kind of player who could break a game open with a single play. He was also solid for a long time, finishing his entire 12-year career with Detroit.