Olynyk immediately showed what he can do by scoring 25 points Sunday in Boston's 95-88 summer league loss to Houston.
Celts general manager Danny Ainge traded up to get Olynyk, shipping the No. 16 pick and two future second-rounders to Dallas for the 13th pick.
Olynyk, who averaged 17.8 points and 7.3 rebounds for the Zags, hit 9 of 12 shots against the Rockets, including 2 of 4 from deep. He added seven rebounds, two assists and two steals.
“He has to not foul so much, and he has to shoot when he's open,” Celts assistant Jay Larranaga, who's coaching the summer league team, told MassLive.com. “He had some shots that he turned down, and he's such an unselfish player that we need to just encourage him to shoot when he's open.”
Olynyk will earn nearly $2 million as a rookie, according to the NBA salary scale.