Knizner just turned 28 and is coming off a pretty disappointing 2022 season where he failed to show why the Cardinals should trust him with playing time behind the plate long-term. Ivan Herrera is right around the corner and still figures to be a valuable big-league catcher, leaving a lot of room to question how Knizner would fit in with the Cardinals' plans.
He is also arbitration eligible in 2024, meaning he'll become a little bit more expensive to have around next season. If Knizner would like to remain on the roster, he'll need to improve both his defense behind the plate and his career .579 OPS at the plate.
I would bet Knizner is replaced by Herrera at some point this season, and we see Knizner as a part of another organization by the season's end.