Tres Barrera doesn't have a spot on Cardinals MLB roster
Tres Barrera is a veteran catcher who is talented enough to at least provide backup duties for a non-contending team. However, he will not find that playing time with the Cards, who already feature Willson Contreras and Andrew Knizer at the position. With Molina potentially coming onto the coaching staff, expect the Cards to prioritize Contreras's defensive ability at the position, rather than having a third catcher on the roster to test him.
Barrera doesn't provide much with his bat at this stage of his career. He accepted an outright demotion to Memphis earlier this season, seeming to suggest he was open to work pretty much anywhere. Barrera had moderate success with the Washington Nationals earlier in his career. Considering he'd be fighting for reps with prospect Ivan Herrera at Triple-A...it's not a great outlook for his potential playing time.