The Royals juggled their roster Wednesday, a day after stunning the Houston Astros with their 9-7 comeback win.
Headed to Kansas City are pitcher Scott Alexander, who was reinstated from the 10-day disabled list, and infielder Ramon Torres, who was recalled from Triple-A Omaha and will make his major league debut Wednesday night.
Headed to Omaha are outfielder Billy Burns and reliever Kevin McCarthy.
Armstrong was placed on the DL with a hamstring strain May 9. The left-hander was 0-1 with a 1.26 ERA and eight strikeouts in 14 1/3 innings (10 games) before his injury.