Nilsson previously played for the Brisbane Bandits and Melbourne Reds in the previous carnation of the Australian Baseball League where he holds the record for all time batting average (.351) and all time slugging average (.661). His brothers Gary, Bob and Ron also played in the competition. He also played in the Japanese NPB and Italian Serie A. He went on to also represent Australia in the 2004 Olympics where they won a historic silver medal, and also represented his country in the inaugural World Baseball Classic in 2006. He spent one season as manager with the Brisbane Bandits during the 2010–11 Australian Baseball League season, before returning to become the incumbent manager since 2014–15. In 2018 he succeeded Jon Deeble as the Australian national baseball team manager.