No. 3: Brett Cecil
Another brutal move from the 2016-2017 offseason, the Cardinals looked to strengthen their bullpen by adding left-handed specialist Brett Cecil to a four-year deal worth $30.5 million.
Although Cecil struggled a bit in the prior season, he had been one of the most consistent and top left-handed relievers from 2013-2015. If Cecil were to regain his from in St. Louis, he would have provided an elite left-handed option to an already strong bullpen.
That would not be the case, though. Across 100 innings in two seasons for the Cardinals, Cecil had an ERA of 4.86, with the especially horrendous 2018 that saw him post an ERA of 6.89 across 32.2 innings.
The contract and performance were so bad that the club released him after the first two seasons, paying Cecil $7.75 million in 2019 and 2020 to not play in St. Louis. He has not pitched in a big league game since, and it is pretty easy to see why.