Players drafted who are under contract with another team generally do not play in the summer league, unless they are first bought out of their contract. This makes sense -- if I'm Zizic' team, why would I let him go play for another professional club for a week, just to have him sent back to me. If he gets injured, I'm on the hook for his salary the next year. And all my other players who are good will ask me to loan them to higher divisions. Without a pretty solid agreement (essentially that the Celtics would buy out the player from his contract if injured, which the C's don't want to do), it just doesn't happen.
Colton Iverson and Marcus Thornton were different. Neither had signed contracts with foreign clubs. That happened after the summer league. The same could happen with Nader, and possibly Bentil, this year.
