He then played 12 seasons in the NBA with the Trail Blazers, New Jersey Nets, New York Knickerbockers, Phoenix Suns, Los Angeles Lakers, and Seattle SuperSonics.

The starting power forward on the Trail Blazers' 1976–77 championship team, he was nicknamed "the Enforcer" because of his primary role on the court, which was best exemplified in Game 2 of the NBA Finals that season.

Lucas played college basketball for head coach Al McGuire with the then-Marquette Warriors for two years, leading them to the NCAA championship game in 1974.

[3][4][5] In the 1975 ABA Playoffs, Lucas averaged 16.3 points, 14.7 rebounds, and 5 assists per game, as the Spirits advanced past the New York Nets in the first round with a 4–1 series victory before losing to the eventual champion Kentucky Colonels in the Eastern Division Finals.

[3] Lucas remained with the Colonels through that team's loss in the semifinals of the 1976 ABA Playoffs to the Denver Nuggets and through the ABA–NBA merger in 1976.

In the 1976–77 NBA season, Lucas led the Trail Blazers in scoring, minutes played, field goals, free throws, and offensive rebounds.

Not only did the team qualify for their first trip to the playoffs that season, but Lucas and teammate Bill Walton led the Trail Blazers past the favored Los Angeles Lakers, sweeping them 4–0 in the Western Conference Finals, and a surprising come-from-behind 4–2 upset victory over the Philadelphia 76ers in the 1977 NBA Finals.

Lionel Hollins missed the shot, both Bob Gross and Darryl Dawkins went up and wrestled for the rebound, and both came crashing to the floor.

As Dawkins ran up court, he threw a punch that largely missed Gross, nailing his own teammate Doug Collins instead.

On February 13, 1981, Lucas set a career high with 6 blocks, while also scoring 31 points and grabbing 13 rebounds, during a 103-100 New Jersey win over the Indiana Pacers.

In his fourteen-year professional basketball career – two in the ABA and 12 in the NBA – Lucas scored 14,857 points and gathered 9,306 rebounds in 1021 games.

Lucas was hired by the Portland Trail Blazers as an assistant coach under Mike Schuler and Rick Adelman during the 1988–89 season.