Herrera has been out of the lineup for Triple-A Memphis due to a left shoulder sprain, Lynn Worthy of the St. Louis Post-Dispatch reports.
Herrera has not played for Memphis since Aug. 4 against Durham. Since being activated from the 10-day injured list July 12, he's slashing .275/.431/.425 with 11 walks, one home run and four RBI across 51 minor-league plate appearances. It's not clear if the 24-year-old catcher will need another stint on the IL.