Heyward, who has played five seasons with the Braves, hit 11 home runs and 58 RBIs in 2014. He also stole 20 bases and earned his second Gold Glove.
Atlanta's decision to move Heyward comes after a difficult year for Braves hitters. The team only scored 573 runs in 2014, second-worst in Major League Baseball.
The Cardinals also receive Walden, a 27-year-old right hander. The reliever appeared in 58 games for the Braves in 2014, finishing the year with 20 holds, three saves and a 2.88 ERA. He was acquired by Atlanta in 2013 after playing his first three MLB seasons with the Angels, including an All-Star year in 2011.
In exchange for Heyward and Walden, the Braves received two young pitchers. Miller, a 24-year-old right-handed starter, finished the year 10-9 with a 3.74 ERA for the Cardinals. In 2013, Miller finished third in Rookie of the year voting after he was 15-9 with a 3.06 ERA in 31 games.
St. Louis also shipped Jenkins, a minor league pitcher, to the Braves. Jenkins, 22, played with the Class A-Advanced Palm Beach Cardinals in 2014.
The Cardinals won the National League Central last season after finishing 90-72. St. Louis advanced to the National League Championship Series, but the Cardinals lost to eventual World Series champion San Francisco in five games.
The Braves failed to make the postseason in 2014, finishing 79-83, 17 games back of NL East champion Washington.
- Stanley Kay