After graduating from Chicago's Lindblom High School and playing collegiately at tiny Aurora College, the 6' 10" forward/center was selected by the Portland Trail Blazers in the fourth round of the 1974 NBA draft.

In what was arguably the best game of his career, on January 30, 1980, Johnson scored 41 points, grabbed 7 rebounds, and recorded 8 assists in a 119–120 loss against the Washington Bullets.

[3] Just a couple weeks later, on February 14 during a 118–114 win over the Cleveland Cavaliers, Johnson set a career high with 6 blocks in a single game, while also adding 14 points, 7 rebounds, and 7 assists.

[5] After finishing the season with a record of 60–22, the Bucks would face the Philadelphia 76ers during the 1981 NBA Playoffs, where Johnson led Milwaukee to a Game 6 win with 22 points, 12 rebounds, and 3 steals.

During his NBA career, Johnson was called "Rubberman" by teammates due his ability to stretch and grab rebounds and block shots, despite his slender frame.