Every year, teams sign a host of depth players who will primarily contribute on special teams. A team would like some offensive or defensive versatility from special teamers, but they will find some specialists that play almost exclusively with the four special teams units.
For the San Francisco 49ers, linebacker Mark Nzeocha was one of those specialists. The team signed him off the Dallas Cowboys practice squad on September 25th last season when they placed Tank Carradine on injured reserve. Nzeocha was inactive three of his first four games, but then appeared in the final nine games.