As good as Castellanos’ bat has been in recent years, his glove is still very much a work in progress. The 27-year-old began his major league career at the hot corner.
However, the defensive metrics were not a fan of his work. In four seasons at third base, Castellanos generated -64 DRS and -7.4 UZR, which are well below average marks.
Those struggles forced the Tigers to move him to the outfield. In four seasons as an outfielder, Castellanos has produced -36 DRS and -11.6 UZR. Similar to his work at third base, his glove in the outfield rates as well below average.
The right-handed hitter is still relatively young at 27 years of age and he has limited experience in the outfield, so there is reason to believe he has room to improve.
However, if the Giants were to add him, they would likely need to pair him with strong gloves in both center field and right field. They may be able to hide his glove in left field.
Of course, there are no assurances that Castellanos will improve in the outfield. As he ages, he could regress defensively and essentially become a designated hitter stuck on a National League roster.
Giants manager Gabe Kapler took an unorthodox approach in filling his coaching staff by adding personnel with relatively limited coaching experience. The theme with these additions was that the coaching staff was going to play a more proactive role in player development at the major league level.
Perhaps, Castellanos would be a good litmus test, albeit an expensive one, in how effective the coaching staff is at helping improve a player’s glove work.
On a smaller note, Castellanos’ offensive profile has red flags as well. Throughout his career, the right-handed slugger has posted a 6.4 percent walk rate against a 23 percent strikeout rate. The low walk rate is especially concerning given that the Giants posted one of the lowest walk rates in baseball at 7.7 percent as a team. That is an area they need to improve upon.
It is a minor red flag, and if Castellanos is able to reach the 20-home run plateau and hit for a high enough batting average, then this will be easy to overlook.
The Giants are still early in their rebuild, but they plan to be competitive in a year or two. That process does not happen overnight. Adding Castellanos would immediately improve the 2020 roster and accelerate the process of building up the roster over time.
Given that Castellanos does not have any draft pick compensation tied to his name, signing him would not hurt the team’s draft strategy in June.
However, marquee free agents have exceeded their projected earnings this offseason, so the Giants will need to be comfortable in going above and beyond what they believe Castellanos’s on-field production is worth. If their goal is to be competitive in the near future, then adding a bat like his will give them an immediate offensive threat.