Manning, 36, a 14-year veteran, said problems with his right elbow as the reason for his decision to leave pro football and return to his home in New Orleans to pursue other interests, which he did not specify.
The teams must be down to 50 players by today.
Brunner was the New York Giants' sixth-round draft choice in 1980. He replaced injured starter Phil Simms and quarterbacked the Giants into the 1981 playoffs. Brunner was traded to Denver after the 1983 season, then wound up with Green Bay.
"Scott has shown he can lead a football team and take them to the playoffs," Cardinal Coach Jim Hanifan said. "We faced Scott before and he played well against us. He'll fit in very well with our football team."
Brunner will back up Neil Lomax at St. Louis.
In another deal, the Packers obtained wide receiver David Verser from the Cincinnati Bengals for a draft choice. The 6-1, 202-pound Verser, who played college ball at Kansas, was the Bengals' first-round draft choice in 1981.
The Dolphins settled on rookie Fuad Reveiz, from Tennessee, as their placekicker and cut Garcia.
Garcia, formerly Green Bay's placekicker, was in the running for the Dolphin kicking job with Reveiz after the Dolphins cut last year's starter, Uwe von Schamann, last Monday.
Coach Don Shula said the two were about even on field goals but that Reveiz, a seventh-round draft pick, had better hang times on kickoffs.
In other action around the NFL:
--Veteran Gary Danielson will be the Cleveland Browns' starting quarterback when they open the season on Sept. 8.
Danielson, acquired from the Detroit Lions on May 1 for a draft choice, has completed 29 of 44 passes for 395 yards and five touchdowns in three exhibition contests.
Rookie Bernie Kosar and Danielson will share playing time in Cleveland's final exhibition game at home against the Raiders on Friday night.
--Denver cut seven players, including former Dallas tight end Jay Saldi.
--New Orleans cut six players including Jimmy Rogers, who was trying to switch to wide receiver after five seasons as a running back, and fullback Tim Wilson.
--The New York Giants cut fifth-round draft choice Tracy Henderson, a wide receiver, veteran tight end Don Hasselbeck and five other players and placed defensive backs Larry Winters and Ken Daniel on injured-reserve.
--The San Francisco 49ers cut sixth-round draft choice Scott Barry, a quarterback, and placed linebacker Fulton Kuykendall, obtained from Atlanta, on injured reserve.
--Tampa Bay cut six players, including guard Glenn Bujnoch and defensive back Anthony Washington, and put 10th-year safety Mark Cotney on injured reserve.
--The Denver Broncos signed offensive tackle Dean Miraldi to a series of one-year contracts. Miraldi, 6-5, 285 pounds, was a second-round draft choice of the Philadelphia Eagles in 1981.