Millington was a first round draft pick (first overall) by Edmonton in the 1990 CFL college draft (obtained from Ottawa for RB Chris Skinner). Millington attended the New York Giants training camp in 1991, and joined Edmonton after his release. Millington played just two games with Edmonton on special teams before he was released. BC signed Millington in September, 1991 and he played four games for the Lions. Millington was used largely on special team by BC in 1992 (8 carries for 52 yards and 6 receptions). In 1993 and 1994, Millington saw his use on offense increase with 52 carries for 276 yards and 38 catches in 1993 and 97 carries for 522 yards and 19 catches in 1994. Millington was named to the Western and All-Canadian All-Star teams in both years at fullback (from 1990 to 1997, All-Stars were awarded to a running back and a fullback instead of the current and previous practice of two running backs). Millington played three more seasons with BC (1995 - 1997) at fullback, winning Western All-Star honours at fullback in 1996 and 1997 as well as being named the Outstanding Canadian in 1997. After 1997, Millington then signed with Winnipeg as a free-agent and played one season and a bit for the Bombers. Edmonton tried to rectify their earlier release of Millington and claimed him on waivers early in the 1999 season and he had his best season rushing with 549 yards. Edmonton promptly repeated their earlier rmistake by releasing Millington in February of 2000. Millington was signed by Winnipeg in March of 2000, but was traded to BC for Antonio Armstrong and Matthieu Beaudoin. Millington's best seasons were the next three seasons (2000-2002) as he ran for his first thousand yard season in 2000 with 1010 yards and followed up with 604 and 740 yards in the following years with over 30 receptions in each year. In 2000, Millington won All Canadian honours at running back and was named the Outstanding Canadian as well as runner-up for the Outstanding Canadian in 2002. Millington retired after the 2002 season, but came out of retirement in 2005 when Toronto ran into injury problems and needed help at fullback down the stretch. Millington finished his career with 5220 yards rushing.