Wacha’s injury is a stress reaction in his right shoulder, which was found following a CT scan and an MRI earlier this week. The 22-year-old continued to feel tightness in his right shoulder while throwing Sunday.
The right-hander is 5-5 with a 2.79 ERA in 15 starts this season.
Garcia, who has suffered with discomfort in his shoulder each of the past three seasons, missed most of last season after undergoing surgery in May 2013 to remedy a labrum tear. This season, the left-hander is 3-1 with a 4.12 ERA across seven starts.
The Cardinals are expected to officially place both starters on the disabled list with corresponding moves on Monday.