So here's a question.
"What?!"
It seems crazy on the surface. From the time Horford started to hit his prime in 2009 through 2013 (before last year was cut short due to a shoulder injury), Horford was 19th in the league in Win Shares per Basketball-Reference.com...He is a two-time All-Star and despite having little to no household name value, is one of the most valuable players in the league, a center that can stretch the floor, defend in the post, shoot, pass, and causes no issues for his teammates.
So why on Earth would the Hawks think about letting him go?
...So if you can't trade Horford for what you need, it doesn't help you to trade him for what you can, and you can't use him to sign a major upgrade. So yeah, Horford will likely continue to be involved in trade talks, because trying to figure out how to work him into a championship picture is one of the more complicated issues in basketball.
They go over the pros and cons of Horford as the team's best player. Pretty interesting, non-biased read.