The Patriots parted ways with CB Sterling Moore on Wednesday. (US Presswire)

Cornerback Sterling Moore was the toast of New England less than a year ago. Now he’s the most expendable piece of a struggling New England Patriots secondary.

In an unexpected move, the Patriots cut the second-year CB Wednesday evening and signed free agent DB Derrick Martin and LB Mike Rivera.

The Patriots had an open roster spot after parting ways with LB Bobby Carpenter Tuesday. In another move, TE Alex Silvestro’s practice squad contract was terminated.

Moore served predominately at nickel back and appeared in all eight games for New England this season. After being released by Oakland, he signed with the Patriots last October, appeared in six regular-season games and made two interceptions.

The 22-year-old rose to prominence during the playoffs when he broke up a potential game-winning pass intended for Baltimore Ravens WR Lee Evans in the AFC title game late in the fourth quarter, which helped deliver New England to the Super Bowl.

New England’s pass defense ranks 28th in the league and has allowed 42 plays of 15 or more yards.

Martin (5-foot-10, 198 pounds) was signed by the Patriots on Aug. 4 but was released before the start of the season. He played 14 games for the Giants last season and finished with 12 tackles.

Nick Underhill covers the Patriots for MassLive.com. Follow him on Twitter @CBSPats or @nick_underhill.