Spencer attended Pocatello High School and was named the Idaho A-1 Player of the Year as a senior in 1998.
Spencer had a notoriously loud and raucous group of fans in high school he named "The Sixth Man" which provided a home court advantage even on away games.
After his freshman year, he went on a two-year mission to Oklahoma, serving the Church of Jesus Christ of Latter-day Saints.
After spending one season with Treviso, mainly coming from the bench, Nelson transferred to Climamio Bologna, also in Italy.
In July 2010 he signed a contract with CB Gran Canaria in the Spanish ACB, where he played with former Utah State teammate Jaycee Carroll during the season 2010/11.