SANTA CLARA — Linebacker Darius Fleming, after two career-changing knee injuries, was released Monday along with wideout DeMarco Sampson and cornerback Dax Swanson to make room for the 49ers’ incoming class of undrafted free agents.

Six signings became official Monday: linebacker Shayne Skov (Stanford), outside linebacker Morgan Breslin (USC), quarterback Kory Faulkner (Southern Illinois), center Dillon Farrell (New Mexico) and offensive tackle Fou Fonoti (Michigan State).

Also agreeing to terms Saturday after the draft but yet to be officially signed is Miami tight end Asante Cleveland.

Fleming arrived as a fifth-round draft pick out of Notre Dame. He tore his left knee’s anterior cruciate ligament on the first day of his rookie minicamp, then sustained an ACL tear in his same knee during last year’s training camp.

Without Fleming, the 49ers’ backup competition at inside linebacker will include Michael Wilhoite, Nick Moody, Chris Borland and Skov. One of those players, barring the signing of a veteran free agent, will need to step up and fill in while NaVorro Bowman recovers from ACL surgery during the first half of the season.