#2 - Adolis Garcia trade
That same offseason, the Cardinals traded away outfield prospect Adolis Garcia to the Texas Rangers for cash considerations. Garcia was coming off a .253/.301/.517 slash line with 32 home runs for Triple-A Memphis, but the Cardinals wanted to create 40-man roster space for Kwan-Hyun Kim.
While Randy Arozarena is a better player than Adolis Garcia, the fact that the Cardinals gave Garcia away for nothing makes this deal even worse.
This year, Garcia is slashing .252/.316/.503 with 11 HR and an MLB-leading 44 RBI. Again, Garcia would have been an excellent bat to have in the Cardinals lineup, but this was another example of the Cardinals giving up too early on a young outfielder.
At least in the Arozarena trade, the Cardinals got back Liberatore and the draft selection that they took Hence with, but in this case, Garcia basically left for free.