Walden did not show up for a recently scheduled rehab assignment and has been shut down indefinitely, Derrick Goold of the St. Louis Post-Dispatch reports.
Walden will see a doctor for another checkup, but it's looking highly unlikely he'll pitch again this season. A strained lat suffered all the way back in March will end up costing the 28-year-old reliever an entire season in the prime of his career.