Richardson was selected in the seventh round (50th overall) of the 1965 AFL draft by the Kansas City Chiefs. He spent two years on the taxi squad, before making the team in 1967. His most productive season was 1968, where he made 22 receptions for 494 yards, 5 touchdowns and a 22.5-yard average per reception.
He was a part of the world championship season in 1969 which ended with a victory in Super Bowl IV. In 1970, although he started 7 games, he only posted 5 receptions for 171 yards and 2 touchdowns.
In 1971, Richardson was used mainly a reserve player behind Bob Hayes and Lance Alworth, registering 4 starts, 8 receptions for 170 yards, 3 touchdowns and a 21.3-yard average per reception. The Cowboys won Super Bowl VI that season.
During his three seasons with the Cleveland Browns, he was mainly used as a reserve player, making a total of 22 receptions for 448 yards and 3 touchdowns. On February 10, 1975, he announced his retirement.[6]