Herrera is unavailable to play Thursday against the Giants due to a back issue, Katie Woo of The Athletic reports.
Herrera's back evidently locked up on him sometime around his arrival at Rickwood Field in Birmingham, Ala. It partly explains why he's not in the lineup, although Pedro Pages has been the Cardinals' preferred option at catcher lately, anyway. At this point, Herrera should be considered day-to-day. St. Louis has a team day off Friday, so he'll have an extra day of rest before the series versus the Giants picks back up Saturday.