Manusky, who played 12 seasons in the NFL, spent the last five years on the Chargers' staff, where he worked on one of the league's top defenses. He spent the previous season with Washington before following coach Marty Schottenheimer to San Diego, where they ran a 3-4 defense similar to the scheme favored by 49ers coach Mike Nolan.

Manusky, who has never been an NFL coordinator, replaces Billy Davis, who was fired last month after two seasons in charge.

Nolan, a longtime defensive coordinator for four NFL teams, was heavily involved with preparing the Niners' defense, yet still dismissed Davis when the unit yielded an NFL-worst 412 points in 2006 after giving up 428 in 2005.

Nolan chose Manusky over Jaguars assistant Dave Campo, former Lions assistant Donnie Henderson and 49ers assistant head coach Mike Singletary, who is a candidate to fill the Dallas Cowboys' head coaching vacancy.

San Francisco offensive coordinator Norv Turner is considered the front-runner for that job in Dallas, which could mean Nolan will have to replace his top three assistants from his 7-9 team. Al Everest was named the 49ers' special teams coordinator last month after Larry Mac Duff left to become assistant head coach at the University of Texas.

Manusky was a special-teams standout during his playing career with Washington, Minnesota and Kansas City. He played in 113 consecutive games at one point before becoming a volunteer assistant in Tampa Bay in 2000.