Heyward, 23, missed close to a month following an emergency appendectomy. He was hitting .121/.261/.259 with two home runs in 69 plate appearances before the injury. Heyward received some MVP votes last season by hitting .269/.335/.479 with 27 homers.
Walden, 25, has allowed seven runs in 13 innings this year (4.85 ERA). He has struck out 16 while walking only three. One of those three was intentional. The Braves acquired the former All-Star closer from the Angels for Tommy Hanson over the winter.
Atlanta had been platooning Jordan Schafer and Reed Johnson in right field during Heyward's absence. With Walden out, right-handed setup duties figure to go to Cory Gearrin and Anthony Varvaro.