Boswell, 34, is 6-foot-2. Pirez is 6-1 and Parkhurst is 5-11.
Atlanta United will next play at D.C. United on Aug. 23, followed by another game at Philadelphia on Aug. 26.
The Five Stripes will open Mercedes-Benz Stadium against Dallas on Sept. 10. It is the first in a stretch of eight games in 24 days.
Parkhurst and Pirez have started all 22 league games this season. Asking them to start each game during the tough home stretch may be too much to ask.
Pirez said he prefers to play every 3-4 days, but his physical style of play can take its toll.