That point has been debunked by BP. There's no solid evidence that a new 3B has any impact on the SS. Besides, even if it were true, Guzman would be losing Ryan Zimmerman and Anderson Hernandez, who are both extremely quality defenders.
How?
What? He's never played at inning at either position.
Of course not, which is the main reason why we should avoid bringing him in. $8 million netted the Rays, Pat Burrell last year. I expect the Red Sox can use the $10 million owed to Guzman, in order to bring in someone who can really impact the standings.
I'm not convinced that Guzman is in the other category. Especially, since he'll be moving to the tougher league.