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-handerwas 0-1 with a 1.26 ERA and eight strikeouts in 14 1/3 innings (10 games) before his injury.
Torres, a free-agent signee out of the Dominican Republic in 2010, will bat ninth and startat second base against the Astros. Torres, 24, was batting .327 with five homers and 34 RBIs for the Storm Chasers this season.
Burns was 0-for-2 in three games with the Royals after being called up for the first time this season Saturday.
McCarthy did not give up a run and allowed only three hits over 6 1/3 innings (four games) for Kansas City this season.