Splitting backfield duties with Kevin Long in Chicago (and in Arizona in 1984), Spencer gained 2,369 yards and scored 23 touchdowns with the Blitz/Wranglers, playing a key role in both teams playoff appearances and the '84 Wranglers trip to the USFL Championship Game.  In 1985 he was surprisingly left unprotected in the Wranglers' merger with the Oklahoma Outlaws, and the Memphis Showboats picked up his contract.  In Memphis he rushed for 789 yards and 3 touchdowns, but he would manage to make 1985 another 1,000-yard year in a manner of speaking, signing with the San Diego Chargers that fall and rushing for another 478 yards and 10 touchdowns.  Spencer's career would continue in the NFL with San Diego, where he played through 1990.

After a few years away from the football scene, Spencer returned to the game as a coach with his alma mater, staying with Ohio State for a decade as the team's running backs coach.  He returned to Chicago, and the NFL, in 2004 joining Lovie Smith's Bears staff as its running backs coach, guiding the team to an NFC championship in 2006.