Harvey was diagnosed with a stress reaction in his right triceps Friday, Paul Sullivan of the Chicago Tribune reports.
Harvey had progressed to throwing off a mound while working his way back from ticeps inflammation, but he reported soreness after Thursday's session. An MRI revealed a stress reaction, which will keep the 31-year-old shut down for the next month. A clearer timeline for his return may begin to emerge once he's cleared to restart his throwing program.