MIAMI (AP) _ Miami offensive tackle Ron Heller announced his retirement Monday, and the Dolphins signed linebacker Jack Del Rio and quarterback Bernie Kosar.

Heller, a 12-year veteran, started seven games at right tackle in 1995. He went on the injured reserve list after having arthroscopic surgery on both knees Oct. 27. He played in 171 career games with 166 starts, including 39 starts with the Dolphins from 1993-95.

Heller, 33, began his career with the Tampa Bay Buccaneers in 1984 and spent four seasons with the club before joining the Philadelphia Eagles in 1988.

Del Rio was the starting middle linebacker the past four seasons for the Minnesota Vikings. He started in nine games in 1995 and finished as the team's fourth-leading tackler with 70, a career-high three sacks, two forced fumbles and one fumble recovery.

Kosar played in nine games and started two for the Dolphins last season. He completed 74 of 108 passes for 699 yards, with three touchdowns and five interceptions.

Terms of the agreements with Kosar and Del Rio were not disclosed.