Coming out of high school, Rivals.com rated Lumpkins as a two star recruit. He decided to commit to American University out of a handful of lower-level division one scholarship offers. Lumpkins enrolled at American University in Washington, D.C., to play for head coach Jeff Jones. During the 2009–10 basketball season, Lumpkins averaged 29.9 minutes per game to go with 13 points and 8.5 rebounds per game. During the 2010–11 basketball season, Lumpkins averaged 13.5 points per game along with 8 rebounds per game while playing 30 minutes per game. Following that season, Lumpkins was drafted by the Kansas City Royals in the 13th round of the MLB Draft. He decided to forgo his senior year at American University and pursue his dream of playing professional baseball. In 2012–13, after one year, away from basketball, he returned to finish his career at American and graduated in 2013. In his career at American University, Lumpkins averaged 13.6 points, 8.7 rebounds, 1.3 blocks, and 1.1 assists in 31.1 minutes per game. "The Lump" was a fan favorite and even had a smattering of supporters called "the Lumpkin Patch."
