No. 14: Konnor Pilkington traded to the Cleveland Indians for César Hernández - July 2021
This trade is still in the process of shaking out in present day, so it will reside near the bottom of this list for now.
When the White Sox were acquiring Hernández, they thought they were going to be landing a contact-oriented hitter who found his power stroke in recent years, swings the bat from both sides of the plate, is a former Gold Glove Award winner and a known clubhouse leader.
Instead, they received the shell of what Hernández once was. A pending free agent, he was a rental acquisition that did virtually nothing for the Sox.
In 53 games post-trade, he went just 45-for-194 (.232 average) with just seven of those hits going for extra bases. He limped to the finish line with an OPS+ of just 68, meaning he was 32 percent below league-average offensively for the Sox.
His struggles didn't even stop there, either. He also posted a -0.3 dWAR along the way, no longer possessing a Gold Glove-caliber glove as he once had.
While a mid-season rental struggling is not enough to warrant any real concerns. it's what Pilkington has done for the (now) Guardians since the trade.
He made his big league debut last year and looked very solid, making 15 appearances (11 starts) and posting a 3.88 ERA and 99 ERA+. He limits home runs at an impressive rate and figures to see some time in the major leagues in the upcoming season.
If Pilkington continues to develop, this trade will come to hurt the Sox for many years to come, especially because he'll be doing it for a division rival.