He played seven seasons (1969–1976) in the now-defunct
American Basketball Association (ABA) and four seasons in the
National Basketball Association (NBA). Calvin began his professional career with the ABA's
Los Angeles Stars, averaging 16.8 points per game in his first regular season to make the ABA All-Rookie Team. Despite finishing 43–41, in the
1970 ABA Playoffs Calvin,
George Stone, and
Craig Raymond, helped the Stars make an unexpected trip to the ABA Finals. On the way there, during a win over the
Dallas Chaparrals in the division semifinals, Mack scored a postseason career high 44 points, while adding 16 assists. In the finals, Calvin averaged 15.8 points and 5 assists per game during a 4–2 series loss to
Roger Brown and the
Indiana Pacers. The following season, he averaged a career-high 27.2 points for
The Floridians, in the process setting the ABA records for most
free throws made (696) and most free throws attempted (805) in one season. During the
1974-75 ABA season, Calvin helped the Nuggets to a 65–19 record by averaging 7.7 assists per game, both of which were best in the league. However, in the Western Division Finals, Denver was eliminated by Indiana in a seven-game series. In 1976, Calvin was traded to the Virginia Squires (alongside
Jan van Breda Kolff and Mike Green) and $250,000 for George Irvine and David Thompson. Wracked with a knee injury that meant he couldn't play with a team disintegrating, he was asked to coach the Squires, which he did for six games. In total during his ABA career, Calvin tallied 10,620 points and 3,067 assists (second in ABA history behind only
Louie Dampier's 4,044) and appeared in 5 All-Star games. Calvin joined the Lakers for the
1976–77 NBA season but saw a sharp decline in playing time. He was able to match the same level of production per minute he reached while in the ABA, though. He spent his four seasons in the NBA with five teams—the Lakers, the
San Antonio Spurs, the Denver Nuggets (which had joined the NBA in 1976), the
Utah Jazz, and the
Cleveland Cavaliers. In the
1978 NBA Playoffs, during his second Denver tenure, Calvin and the Nuggets made it to the Western Conference Finals, before being eliminated by the
Seattle SuperSonics. Calvin retired in 1981 with an NBA career scoring-average of 7.0 points per game. ==Legacy==