He WAS a good defender. There is concern that his arm is no longer fit for SS. This is not "well Xander has a bad arm too" but rather "if you put Story at SS, he may be much more likely to wind up on the DL/IL."
I'm more concerned about Story's home/away splits though.
I wouldn't have signed him. It's more than a 50/50 chance that this contract doesn't work in the Sox's favor.
According to NJ Advance Media, several scouts around the league believe that Story is better suited to play second base due to his diminished arm strength. Story has dealt with several elbow strains over the last few seasons, which is why a shift to second could help reduce the wear-and-tear on his arm.
If his throwing arm is toast, maybe him getting to a ball Xander wouldn't is irrelevant.
From MLB.com:
Statistician and writer Henry Chadwick gets credit for inventing ERA in the mid-to-late 19th century. His thinking was that win-loss record simply didn't go far enough in determining the mark of a good pitcher.
@JonHeyman
After losing out on Freddie Freeman, Red Sox are taking a look at Trevor Story. One catch: he would likely have to play 2B as 2-time WS champ Xander Bogaerts is the SS. Other possible options for Story: Cards, Twins, Astros, more.