Not to be a Debbie Downer or anything, but the exciting Gordon Hayward signing also comes with some drawbacks. In order to afford the max money Hayward will receive from the Celtics, they will likely have to trade one of Marcus Smart, Jae Crowder, or Avery Bradley.
While there could potentially be a way to avoid departing with any of these guys, it would require a lot of maneuvering and moving pieces, and would still be a close call. It would likely involve shedding the rookie contracts of Demetrius Jackson and Jordan Mickey, stashing Guerschon Yabusele again, and ditching role player Terry Rozier.