Danny wanted to use Horford to convince Durant to come to Boston. He signed Horford at the market rate, then lost on Durant.
Horford is overpaid, as are many free agents.
I'm sure Danny would include him in a trade if one becomes available. Until then, he'll be a useful big man that helps run an offense.
This is probably my take on Horford as well. I am happy to have him, was excited when we signed him, and have been mostly pleased with his play throughout his first two seasons with the Cs. But, I don't consider him untouchable and think that Hayward will replace a lot of what he does when he is finally healthy.
Like others, I wonder about what kind-of pay cut he will take when he is a FA again. It is entirely possible he opts out of his contract after next season and signs on with another team for [near] max dollars knowing the Cs won't be able to do the same. He doesn't seem like the type, but you never know.
Also, I don't think it is totally fair to assume the Cs would be a train wreck or wouldn't be as well-off if we didn't have Horford - Ainge has earned the benefit of the doubt in his team building. I think everybody agrees that Horford is better than nothing.
Until 'something' happens, I am going to just go ahead an keep enjoying Horford and the rest of the Cs play well and hope they can make a long playoff run!