Xander Bogaerts made it clear that he didn't feel comfortable at 3rd after the 2014 season. You don't take a player with star potential and put him somewhere he's not comfortable. It would be like making a phenomenal athlete like Moncada a designated hitter at the age of 21.
Do you seriously think that Jose Iglesias, who is at best, cocky to a fault, would be happy as a back up SS at this point in his career, never getting a chance to be a starter? The answer is no.
The Red Sox probably have one of the best medical staffs on the planet, so yes, they were concerned that he was an injury risk, especially with his shins. It was written about publicly. Google it if you don't believe me.
Defensive metrics are certainly argumentative & the farthest thing from definitive, but I'm glad you found some that help him look good. He's definitely the first SS that I heard that Pedey wanted to strangle though.
I really didn't want to crucify Iglesias, I just can't understand how a Red Sox fan could ever have an issue with that trade.