By now you know that the
Chicago White Sox
starting with the run-up to the 2017 season undertook an almost complete teardown, and the early returns on said teardown have been highly promising. Added to the system via trade in recent months are high-ceiling talents like
, Luis Basabe, and … we could go on. Add those names to a few promising youngsters already in the fold (
, most notably), and the White Sox have an excellent long-term outlook.
Eliminated from contention and presently on pace for 97 losses, the club is squarely focused on the future.
Speaking of which, Sox GM Rick Hahn and his lieutenants, for all the good work they’ve done during this rebuild, still have some critical decisions to make — decisions that will have a bearing on whether the club realizes the potential they’ve been assiduously building. Specifically, three forthcoming decisions stand out. To wit …
1. Do you trade
The 30-year-old slugger is enjoying quite a renaissance. In 2017, he’s batting .308/.359/.559, which translates to an OPS+ of 142, with 31 homers.
That’s big because Abreu was showing signs of decline prior to this season. In his excellent rookie campaign of 2014 he put up an MLB-leading 173 OPS+. That figure dropped to 135 in 2015 and then to 125 in 2016.
This season, however, he’s reversed course to an impressive extent. These also look like genuine improvements. This season, Abreu’s increased his fly-ball rate while also increasing his percentage of hard-hit balls. In related matters, Abreu’s doing a much better job in 2017 of laying off pitches outside the strike zone. That all makes his improved production — and halted decline — understandable and perhaps sustainable.
To get a better handle on the sustainability of Abreu’s 2017 gains, we’ll turn to an advanced metric called expected weighted on-base average (xwOBA). xwOBA grows out of wOBA, which assigns proper value to every possible offensive event that happens while a batter is at the plate. Those proper valuations of singles, doubles, homers, walks, etc., distinguish wOBA from more traditional measures like AVG, OBP, and SLG. Also, for simplicity wOBA is scaled to look like OBP, which means that, say, .400 is elite and .290 is pretty poor. For instance, Babe Ruth is the all-time leader with a patently absurd wOBA of .513.
All of that brings us back to xwOBA, which is an estimation of what a hitter’s wOBA should be based on things like exit velocity off the bat and launch angle. xwOBA attempts to strip away luck — bad or good — and defensive play from wOBA and identify a hitter’s baseline skill. It’s useful for getting an idea of how a hitter figures to perform in the near-term future. Basically, if a hitter’s xwOBA is significantly lower than his wOBA, he’s probably going to come back to earth at some point. On the other side of things, if a hitter’s xwOBA is…