Ivan Herrera isn't getting enough playing time
Much like Michael Siani, Pedro Pages was brought in due to significant injuries and took over a highly important position. Pages played well enough for the team to stay in contention, but just like Siani, it's time for Pages to return to a bench role. It's true that Pages has been ridiculously good in the clutch, with many special moments throughout his limited run, but overall he's been below league average.
He's had fine offensive production for the catcher position, but Ivan Herrera has much more potential as a backup to Willson Contreras. With Contreras out again, Herrera should've been the one taking over as the primary starter, but instead he's been relegated to a platoon bat against left-handed pitching while Pages draws the majority of starts behind the dish.
Pages' defensive numbers, while better than Herrera's, are a bit overstated. His framing numbers have dipped a bit, and he's not much better at throwing out baserunners compared to Ivan Herrera. Pages is by far the superior defender compared to Herrera, but it's not good enough to warrant starting him over Herrera every day. Herrera's offensive potential is much stronger than Pages', and with the season lost, it's more important to give the limited amount of reps to the player with the higher ceiling going forward.
Once again, it looks like the Cardinals are mismanaging a bat-first catcher due to their less-than-stellar defense. Even if the Cardinals don't see Herrera as a long-term solution as a backup catcher going forward, benching him for this stretch decreases his potential trade value. Ivan Herrera will certainly use the offseason to improve as a catcher, but not allowing him to start over Pedro Pages in the present moment is quite wasteful.