#1: Nathan Eovaldi is now a Cy Young candidate
Finally, on this list, we have probably the most painful one as a Sox fan. Many fans knew Nathan Eovaldi had it in him to be a quality starter in this league, which he had been for Boston and a few other teams throughout his career. However, the pace he is now playing at is that of a Cy Young candidate, which makes this loss tough.
In his four full seasons with Boston, Eovaldi had made 73 starts with 407.2 innings pitched, registering a 4.15 ERA and 1.268 WHIP. He accrued 420 strikeouts to 97 walks, with 9.3 strikeouts per nine innings which is very good. Injuries near the end of his Boston career were what concerned Bloom seemingly, and ended up making Eovaldi move on to Texas.
Now, with the Rangers, he has pitched nine starts and 60.1 innings, putting together a 2.83 ERA, 0.994 WHIP, 1 complete game shutout, with 61 strikeouts (9.1 per nine innings) to 10 walks (1.5 per nine innings). As of right now according to the ESPN Cy Young tracker, he is currently ranked 4th in their predictor.
At the time, letting him walk made sense due to the injury and seemingly poor production post-recovery. However, a chance of scenery has allowed Nathan to turn into one of the game's best current pitchers, which definitely stings for Boston in the short term.