The Red Sox have three major-league catchers on their team. The issue is that it's unclear at this early stage just how productive any of the three are going to be. Blake Swihart is entering his first full season in the majors after a promising but up-and-down rookie campaign. Christian Vazquez has tremendous defense and hit well enough in 2014, but missed 2015 thanks to Tommy John surgery.
Then there is Ryan Hanigan, who has the lowest ceiling of the group given he's an established veteran, but you also know what you're getting out of him at this point. It's understandable, then, that there would be teams looking to trade for Hanigan later in the season, according to the Boston Globe's Nick Cafardo. It seems unlikely the Sox would deal him, though.
For one, there's the above sentiment that the Sox know what they can expect out of Hanigan, whereas their other two options remain unproven in the long run. Then, there is the fact that none of the three runs a pitching staff as well as Hanigan does right now -- Vazquez might, and maybe even someday soon, but Swihart is still acclimating to all that a big-league catching gig entails.
Plus, as Cafardo mentions, Hanigan has worked well with the pitchers themselves. He's also an asset to the Red Sox in terms of prepping Swihart and Vazquez for a future in which they are the two primary catchers on the roster, which is especially useful for Swihart, who does not have Vazquez's skills or experience behind the plate even if he has plenty of tools himself.
It helps, too, that Hanigan has a $3.75 million option for 2017 -- there's no rush on moving him now, while the catching situation is unsettled. Maybe in a year they deal him. Maybe in a year, they deal one of Swihart or Vazquez instead, and then find a new backup after 2017. Regardless of which it is, if it's even either, chances are good Hanigan is staying put both for now and well into 2016, if not for the entirety of it. Catching depth is not a luxury, so much as a necessity, and the Sox are currently in a good place behind the plate.