As a sophomore in 2006–07, Mercer started all 23 games for Georgia before suffering a right ACL injury that forced him to miss the final 10 games of the season. He was the second leading scorer on the team at 13.6 points per game. Prior to his injury, Mercer was leading the team in scoring and minutes played and was ranked 18th in the SEC in scoring, 14th in assists (3.6), eighth in steals (1.70) and 13th in assist/turnover ratio (1.43). He earned SEC Player of the Week honors once and came within two rebounds against Jacksonville of becoming first Bulldogs player in history to achieve a triple-double.