Day joined the Arkansas Rimrockers for their inaugural season in the ABA basketball league in 2004-05. In their only season in the league, the Rimrockers had a record of 32-5, defeating the Bellevue Blackhawks 118-103 in Alltel Arena for the league championship. Day finished the game with 32 points and 6 steals. Day was named 1st Team All-ABA and was an ABA All-Star. Day helped Rayyan (Qatar) win the 16th FedEx FIBA Asia Champions Cup in 2005, scoring 24 points in the victory over Fastlink (Jordan). Day signed a free agent contract with the Detroit Pistons, but was released in training camp. Day returned to the ABA for the 2006-07 season, playing with the Arkansas Aeros. He was selected to play in the ABA All-Star Game on January 28, 2007, in Halifax, Nova Scotia. Day was averaging 21.4 points per game prior to the All-Star Game. Day also had a stint playing for the Harlem Globetrotters.