#3 - Randy Arozarena trade
Following a brief but productive stint with the Cardinals during the 2019 season, St. Louis shipped outfielder Randy Arozarena, first baseman/outfielder Jose Martinez, and a Competitive Balance Round A draft selection to the Tampa Bay Rays for top prospect Matthew Liberatore, catcher Edgardo Rodriquez, and the Rays' Competitive Balance Round B draft selection.
Arozarena has gone on to rake as a Ray with a career 134 wRC+. In 2023, the outfielder is slashing .312/.394/.552 with 10 HR and 35 RBI while leading the best team in baseball to this point in the season.
While Randy has gone on to find major success in Tampa Bay, the Cardinals are still struggling to find consistent production from guys like Dylan Carlson and Tyler O'Neill. Had the Cardinals deal one of those two instead, this deal would feel much better, but instead, they gave up easily the most valuable outfielder they had at that time.
This trade does have the ability to age better if some things continue to go well for the Cardinals. Despite a few down seasons in recent years, Liberatore has been on the upswing as of late and just beat Corbin Burnes in a head-to-head matchup while spinning five scoreless innings.
The Competitive Balance pick that the Cardinals received from the Rays turned out to be Tink Hence, meaning the Cardinals may end up turning Arozarena into two very good pitchers for their club. Should that end up being the case, St. Louis will not have as much regret with this deal.