Since they didn't rule out their stashes for the season, the Celtics didn't have enough cap space to sign Zeller because unsigned first round picks still have cap holds, so they used his Bird rights instead. (This is wrongly reported in some places as cap space being used.) Since the team technically went over the cap to sign Zeller and gave him a large enough raise, he is not eligible to be traded until January 15. This rule is a replacement for the base-year compensation rule that made it difficult to trade recent free agent signings.