LAS VEGAS – The early returns on Ante Zizic didn’t look all that promising.

“He can play better than he has the first two games,” Austin Ainge, the Celtics director of player personnel, told CSNNE.com last week. “He’s done some good things but he’ll play better.”

And that faith was validated on Sunday as Zizic’s strong game was among the many factors that contributed to Boston’s 70-64 win over Portland in summer league action.

Zizic had a near double-double, finishing with nine points and 11 rebounds.

“Today I think I play really good,” Zizic said.

Following the win, Zizic acknowledged it’s going to take him a little bit of time to adjust to the NBA game.

“Like I say, I need to adjust, a little bit of time. This is my fifth game here, and also … I expect a little bit more from myself,” he said.

While the execution hasn’t always been there for Zizic, it’s not due to a lack of effort.

He came to the league with the reputation of being a physical banger.

Five summer league games into his pro career with the Celtics, playing with a high level of physicality has indeed been one of the constants for this 20-year-old.

“He plays hard and he’s physical,” Ainge said. “Those are his strengths.”

But he can do more than bang on bodies, for sure.

In his short time with the Celtics, he has shown a certain comfort level while shooting a left or right-handed, over-the-shoulder hook shot in the lane.

Celtics assistant coach Walter McCarty, who is coaching Boston’s Las Vegas summer league team, said he went into tonight’s game wanting to get Zizic more involved.

“Getting him rolling to the basket, post-ups, so he’s not just setting screens,” McCarty said. “I think it really helped him out.”

And that in turn helped the Celtics (2-0) remain undefeated with one more game – against Philadelphia on Tuesday – before teams are seeded for the double-elimination portion of the Vegas summer league.