ALAMEDA, Calif. (AP) - The Oakland Raiders have signed former Chicago linebacker Nick Roach to a free-agent deal to bolster their depleted defense.

Roach's agent, Josh Wright, confirmed the deal on Friday. Roach is the second linebacker signed by Oakland this week, following a three-year, $6 million deal given to Kaluka Maiava on Wednesday.

The Raiders began the free agency period this week with just four returning starters on defense. They lost two of their top performers in free agency when defensive tackle Desmond Bryant signed with Cincinnati and linebacker Philip Wheeler signed with Miami. Oakland also released defensive back Michael Huff.

Roach is expected to replace former first-round pick Rolando McClain as the starter in the middle.