I'm astounded that none of the other 29 teams in the NBA have given Sullinger -- or Zeller -- an offer sheet. Even if only to mess with Ainge's ability to go after major FAs.
Because it wouldn't mess with Ainge's ability at all. If they sign him to an offer sheet, their cap space is tied up for three days while the Celtics debate what to do. The Celtics, on the other hand, would just have the normal cap hold that they already have. And really, since they can't submit that offer sheet until July 7th, it'd be nearly a week the other team would have to keep the cap space available, perhaps only to see it ultimately be wasted if the Celtics match. Unless you know you've got nothing better to do with the money (Nets, Mavs), you might as well wait until the best unrestricted free agents are gone, especially if some of their RFA's might become unrestricted themselves before long.