Jake Diekman, a left-handed relief pitcher, is set to join the White Sox bullpen.
Diekman, 35, has a 4.23 ERA, a 4.62 xERA, and a 4.97 FIP in 38 1⁄3 innings this season. FanGraphs, which uses a FIP-based formula to calculate pitching value, says that Diekman has been worth -0.5 WAR in 2022. Throughout his career, though, Diekman has accumulated 5.1 fWAR by having a 3.58 FIP.
With Aaron Bummer and Garrett Crochet on the injured list, the White Sox have been in need of a reliable left-handed pitcher. Diekman’s splits have been massive this season, with left-handed batters only slashing .188/.316/.250, while righties have slashed .212/.395/.447.
According to Baseball Savant, Diekman’s whiff rate is in the 90th percentile among MLB pitchers, and his strikeout rate is in the 86th percentile. On the other hand, control has been a major issue, as his sky-high walk rate (7.0 per nine innings) is in the first percentile. Given opposing hitters’ low batting averages, if Diekman can reduce his walk rate, he can be a valuable asset in the bullpen.
Reese McGuire, 27, is on his way to Boston. McGuire was a poor hitter, as he slashed only .225/.261/.285 with a 55 wRC+. However, his strong defense behind the plate made him a somewhat serviceable player, as he accumulated 0.4 fWAR. Even with his defense, though, given Seby Zavala’s performance (.296/.340/.439, 122 wRC+, 1.1 fWAR), McGuire was nonessential. Both of Grandal’s backups were out of minor league options, and keeping Zavala over McGuire was the right call. In this case, the choice was either to DFA McGuire or get someone in return, and the front office chose the latter.