It is very hard to build a true contender around Durant this off season. Danny knows this it is crystal clear. The free agent market is weak. The C's are loaded with young, cheep talent but they need a year of growth. You have to take Durant now obviously if he is willing to come. It is going to hurt though if he does because you will have to trade away a lot of the young talent to build around him. You must cut loose all of Sully, Amir, Jerebko etc. just to sign both K.D. and Horford.
If you wait a year you can hit 2017 with a ridiculous amount of cap room, in a great free agent market, you can maintain most of your best assets and build a more viable contender. The best case scenario is also the most likely that K.D. goes back to O.K.C. this year. Hopefully he then joins the C's next year.
Patience could result in the Celtics building a contender while also simultaneously building for the future. If Durant comes this year that thought will disappear quickly as Brown, 2017 Brooklyn, 2018 Brooklyn all likely are traded to add immediate help.
For the 2017-2018 season Westbrook, Durant, Paul, Hayward, Griffin, Curry, Milsap, Ibaka etc. could team up together and pick a destination like Boston and you wouldn't have to give up anything or a lot less anyway and build a true contender.