49ers keep shoring up defense after last week’s Buckner trade

Barring the arrival of a top-flight defensive tackle or cornerback, the 49ers defense does not have many vacancies. Instead, as the second week of free agency commences, improving depth is likely the focus, such as Monday’s move to add linebacker Joe Walker.

Walker defects after four years with the Arizona Cardinals to not only compete for a backup role at linebacker but to assist on special teams.

The 49ers have yet to announce Walker’s signing, as first reported by NFL Network.

Walker, 27, was a 2016 seventh-round draft pick out of Oregon, where he played with Arik Armstead and DeForest Buckner, the latter of whom got dealt by the 49ers to the Indianapolis Colts last week.

Walker began his career with the Philadelphia Eagles, and started the Cardinals’ final 10 games last season at inside linebacker. He presumably slides into a role vacated by Elijah Lee, who the 49ers did not tender as a restricted free agent.

A week ago, the 49ers agreed to re-sign defensive end Ronald Blair, and they officially confirmed that move Monday with an accompanying statement from general manager John Lynch.

“We are thrilled to have agreed with Ronnie Blair to continue with the Niner family,” Lynch’s statement began. “Ronnie is a great teammate, who has developed into a key contributor to our defense.

“His versatility and playmaking ability along with his strength of character off the field make him special. Ronnie’s work ethic makes us confident he will return to form this season.”

Blair is coming off anterior cruciate ligament replacement. He can help shore up a defensive front that lost Buckner but re-signed Armstead last Monday.