Let me begin this post by saying that I'm not writing this to bash Starlin Castro in any way. He's had a rough enough time of things this year to begin with, and I certainly don't intend to pile on.
The facts, though, speak for themselves. By just about any measure Castro has been the worst regular offensive player in the major leagues this year. You could perhaps live with that if he were providing above-average defensive value, but he's not doing that, either. The Cubs were right to bench him, as his presence in the lineup was not helping the team. Essentially, for the last three games of the Giants series, the ones Castro spent on the bench, his bat was replaced by Kyle Schwarber's, a significant upgrade.
Apart from the last four weeks of 2014, which he missed with an ankle injury, these three games represent the longest bench stint of Castro's career. Given that the team is winning, and scoring more runs, without him, it seems likely he'll remain anchored to the bench most of the time. He was on deck at one point in the Giants series to pinch-hit, but never did get into any of the games he didn't start.
Castro is under contract for the next four years for approximately $41 million (that includes a $1 million buyout for 2020). His age 26 through 29 seasons, you'd think, should be the most productive of his career, likely the reason Theo & Co. signed him to that contract extension three summers ago.
Thus I put to you the question: What can the team do with him, both in the seven weeks or so remaining in the 2015 season and also beyond?
Could they move him to second base? Sure, but without quite a bit of work there I'm not convinced his defense would be any better than it is at shortstop. Plus, the Cubs have Javier Baez potentially ready to take over that position in 2016.
Could they move him to center field? No one's really mentioned this, but Castro does have a good arm and other middle infielders have been moved to center field with success. This assumes he'd recover offensively and that the Cubs don't re-sign Dexter Fowler for 2016 (and possibly 2017).
Can they trade him? Sure, but at this point some team's going to have to take a chance on that $41 million (or the Cubs would have to kick in some of the money). That won't happen until this offseason, most likely, so the Cubs might have to live with a bench with an almost-completely-unproductive player for the next three weeks until rosters expand.
Castro is still just 25 years old, but has over 3,600 big-league plate appearances and 943 career hits. Only 40 players in MLB history have had that many hits through their age-25 season, and if you look at the entire list of those players you'll see that there really isn't a single one who didn't have at least a long and productive big-league career.
I can't believe Castro is the outlier to that group and won't. Even with his bad season in 2015 he still has 8.3 career bWAR, hinting that he could still be productive beyond this year.
What would you do with Castro?
I ask one thing only: please be respectful. Yes, he has not played baseball well this year. He's still a human being. We all deserve the same respect.