The 49ers' top five cornerbacks from a year ago will return for the opening of the offseason program on Monday.
Three-year veteran Tramaine Brock, who the 49ers like enough to tender a one-year, $1.323 million contract as a restricted free agent, will sign the deal on Monday, a source said.
Brock was the 49ers' No. 4 cornerback last season behind Carlos Rogers, Tarell Brown and Chris Culliver. Cornerback Perrish Cox was the dime back as the No. 2 slot cover man.
The competition at cornerback is expected to be fierce this offseason, as the club added veteran Nnamdi Asomugha with a one-year contract that contains no guaranteed money. Asomugha will likely have to win a starting job to make the team because backup cornerbacks are expected to make large contributions on special teams.
[RELATED: 49ers offseason scorecard]
The 49ers return nine starters on defense. Glenn Dorsey was signed to take over at nose tackle on base downs following the offseason losses of Isaac Sopoaga and Ricky Jean Francois.
Craig Dahl, who started 16 games for the St. Louis Rams last season, is currently atop the depth chart at free safety. But the 49ers are expected to draft a player to compete for the right to replace Dashon Goldson, who signed a lucrative deal with the Tampa Bay Buccaneers at the start of free agency.
DEFENSE DEPTH CHART
LDT -- Ray McDonald, Will Tukuafu
NT -- Glenn Dorsey, Ian Williams, Lamar Divens
RDT -- Justin Smith, Demarcus Dobbs, Tony Jerod-Eddie
LOLB -- Ahmad Brooks, Parys Haralson, Cam Johnson
ILB -- NaVorro Bowman, Dan Skuta
ILB -- Patrick Willis, Michael Wilhoite, Nate Stupar
ROLB -- Aldon Smith, Parys Haralson, Darius Fleming
LCB -- Carlos Rogers, Nnamdi Asomugha, Perrish Cox
RCB -- Tarell Brown, Chris Culliver, Tramaine Brock
FS -- Craig Dahl, C.J. Spillman, Michael Thomas
SS -- Donte Whitner, Trenton Robinson, Darcel McBath
SPECIAL TEAMS DEPTH CHART
Punt return -- Kyle Williams, Perrish Cox, LaMichael James
Kickoff return -- LaMichael James, Kendall Hunter, Kyle Williams, Ricardo Lockette
Punter -- Andy Lee
Kicker -- Phil Dawson
Holder -- Andy Lee
Long snapper -- Brian Jennings