6. Giovanny Gallegos trade (2018)
The Cardinals' trade of Luke Voit to the New York Yankees for Chasen Shreve and Giovanny Gallegos is a lesson that it usually takes a few seasons to be able to accurately judge a trade. Voit went off in the abridged 2020 season, leading the major leagues in home runs and causing dismay among Cardinals fans. But to the Cardinals' credit, they saw something in Gallegos, and the deal has unquestionably swung heavily in favor of the Cardinals.
While Shreve was unspectacular with the Cardinals and departed in free agency after 2019, Gallegos became a stalwart in the Cardinals bullpen. In a normally volatile position in terms of pitchers' yearly performance, Gallegos has been remarkably consistent, with a 2.75 ERA and 302 strikeouts in 249 innings during just over five seasons with the team. He was the Cardinals' primary closer in 2021, netting 14 saves that year and in 2022 until he was unseated by Ryan Helsley.
After Voit's spectacular 2020, he fell back to earth and hit only .239 with 11 home runs in 2021. He subsequently played with the San Diego Padres, Washington Nationals, and Milwaukee Brewers the following two seasons and hit only .225 with 22 home runs with those teams.
While Voit proved to be a meteor streaking across the sky, shining brightly and crashing violently, Gallegos showed himself to be the real deal, and he has been one of the pillars in the Cardinals' bullpen for several seasons.