He competed in four games, starting two, before suffering a season-ending knee injury on December 21 against Wright State. While out injured, Mercer again ran into trouble. On January 23, 2009, he was arrested for the second time in four months: the first being in September 2008 for public consumption of alcohol, and the second being for marijuana possession. Arrested with him was teammate Anthony Crater, who were both charged with misdemeanor possession of marijuana. Both were suspended from the team indefinitely. It seemed his career, at Georgia and USF, would be remembered for injuries and dismissals, and for the disappointment of missed opportunities. But coach Stan Heath kept Mercer on scholarship, hoping he would stick around and earn his degree, and after Mercer graduated in August 2009 and fulfilled the legal requirements of a pretrial intervention program to get a misdemeanor drug charge dropped, Heath took a chance by allowing Mercer back on the team for the 2009–10 season. Heath's decision paid dividends, as Mercer became a key part of the Bulls' emergence in 2009–10. In February 2010, Mercer expressed how grateful he was to be part of a team making a run at the NCAA Tournament: "Coming back has been a blessing. I'm grateful that Coach Heath and the coaching staff gave me another chance, and that's why I play my heart out every game. When you have a coach that's willing to go out on a limb for you, it makes you want to work that much harder for them." In 2009–10, Mercer played in all 33 games for the Bulls, starting 30 of them. He ranked fifth on the team with 9.2 points per game while also adding 4.5 rebounds in 28.6 minutes per contest. He also finished third on the team with 48 assists and second with 44 steals. On January 5, 2010, he had his first career double-double with 10 points and a career-high 10 rebounds against Notre Dame. During the season, he had two 19-point games, a season high. After earning a degree in criminology, Mercer began working on a second degree in communications. In November 2010, Mercer joined the Halifax Rainmen as a non-contracted training camp invite. He helped the team go 3–1 over four preseason games between December 10 and 19, and made his regular season debut for the club in the season opener on January 2, 2011, scoring 14 points in a 109–99 win over the Vermont Frost Heaves. Mercer left the team on February 15 because of undisclosed family reasons.