ENGLEWOOD, Colo. –Four players who were various forms of free agents this offseason officially signed contracts to return to the Broncos on Monday.

Defensive tackle Mitch Unrein, who will enter his fourth NFL season, signed his restricted free-agent tender. Unrein matched his career high with 20 tackles last year, during which he appeared in all 16 games for the second straight season.

The other three players to sign were cornerback Tony Carter, safety Duke Ihenacho and linebacker Brandon Marshall, who were all exclusive-rights free agents.

Carter played 12 games, including a pair of starts last season and made 13 tackles with one interception and six pass breakups.

Ihenacho started 14-of-15 games played and led the team's defensive backs with 72 tackles in 2013.

Marshall competed on Denver's practice squad for the first 16 weeks of the 2013 season before being signed to the active roster on Dec. 24. He played one regular-season game and made one tackle.