Boston Celtics

Mercer was selected with the sixth overall pick of the 1997 NBA draft by the Boston Celtics and was reunited with fellow Kentucky teammate Antoine Walker, and Rick Pitino, his coach at Kentucky who had just become the coach of the Celtics. Prior to Mercer's drafting, Pitino was recorded as saying that he did not envisage Mercer as having the necessary talent to be selected very high. Some felt this was just a ploy to scare the other teams away from him so as to increase the likelihood of Mercer being available by the time the Celtics got an opportunity to make their draft selection.^[2] It turned out it was.^[3]

Denver Nuggets and Orlando Magic

After two seasons in Boston, Mercer was traded by the Celtics along with Popeye Jones and Dwayne Schintzius to the Denver Nuggets for Danny Fortson, Eric Williams, Eric Washington, and a future draft choice. He played 37 games for Denver in 1999–2000, then played the final 31 games that season with the Orlando Magic due to a trade.

Chicago Bulls

Mercer left after that season, signing as a free agent with the Chicago Bulls the next year.^[4] He averaged 19.7 points per game in his first year with them.

This was Mercer's career high in points per game and was the second leading scorer on the team. ^[5]

Indiana Pacers

Despite Mercer's 16.8 points per game in 2001–02, he was traded midway through the season alongside Brad Miller, Ron Artest, and Kevin Ollie to the Indiana Pacers for Jalen Rose, Travis Best, Norman Richardson, and a second-round draft pick. In Indiana, he served merely as a reserve player and his play declined rapidly over his one-and-a-half-season stint with the club.^[6]

San Antonio Spurs

Before the 2003–04 season, Mercer was traded to the San Antonio Spurs in a three-team trade that again involved Brad Miller and the Sacramento Kings' Hedo Türkoğlu.^[7] After playing 39 games with the Spurs, he was released.^[8]

New Jersey Nets

Prior to the 2004–05 season, Mercer signed with his seventh NBA team, the New Jersey Nets.^[9] On August 15, 2005, prior to the 2005–06 NBA season, he was waived by the Nets to avoid the league's luxury tax as part of the new labor agreement.^{[citation needed]}