LAS VEGAS – Ante Zizic is a big man, which has its pros and cons. There were few players he competed against in Europe who could push him around and make him uncomfortable. But now he’s playing in the NBA, where everyone is faster, stronger and more tenacious.

So it wasn’t shocking when Zizic had a rough start in his first game in Vegas, not even playing in the second half of his fourth game in six days. But he woke up against the Portland Trail Blazers Sunday, finding his rhythm start to finish in a 70-64 win. The rookie finished with 9 points, 11 rebounds and 4 blocks in 27 minutes, after playing just 10 minutes the previous night.

Zizic got off to a solid start, setting good screen and rolls to work the defense and open looks for off-ball player like Jaylen Brown.

Starting off strong from behind the arc pic.twitter.com/NYR41diNNx — Boston Celtics (@celtics) July 10, 2017

But as the game went on, as has been the trend, Zizic started to look a little sluggish and behind the play. His solid screens turned into light breezes while his trips up and down the floor in transition slowed below the posted speed limit. In all of his intensity and effort throughout the first half, he started to wear himself out.

“He's just playing too hard right now,” coach Walter McCarty told CelticsBlog after the game. “I've got to get him more rest early on because he is going all out for everything. Every time there is a rebound, he is running back to chase it, even if it's out of reach.”

Zizic embraces the battle, but he will have to learn how to pick them. He finished with a solid stat line but somewhat coasted through crunch time as Caleb Swanigan and Pat Connaughton helped the Blazers climb back.

Ante is a brute, but being powerful at the NBA level requires both technique and strength. He has the physical power down, but he’s going against guys who know how to use leverage, timing, and footwork to get their way. It’s all a little faster than Ante is used to and the playing style is a little different, something he is confident will be nailed down by the time the real games begin.

"The game is much faster," he said. "But for me that's not a problem. After training camp I will be ready 100 percent for this style of game. And of course, there's a lot of [iso] here. They prefer a game of one-on-one and I'll find my role."

Coach McCarty sees it as learning how to leverage in the NBA, where players are more athletic and initiate contact under a different officiating environment.

“Here in the NBA, we use our arm on you. He’s gotta get used to that,” McCarty told CelticsBlog.

The Celtics are working him into their DHO-based system, using bigs to hand off to wings at the top of the key and elbows. This works when you stay low, use your body as a shield, and make the defense treat you like a ballhandler. It’s a relatively new concept for him and it’s causing a lot of issues.

“Right now he has to get lower in the triple threat,” Walter said to the media. “He’s just standing straight up and they’re pushing and not allowing him to run the play. So we’re just getting him comfortable with that and just get used to playing in a triple threat and playing up top.”

Zizic is also getting an education on how to contest drives, acclimating to rotating into contests from driving wings while also reading post ups by bigs. Zizic is going for the verticality play most of the time, but he was exposed by Swanigan late when Caleb went to up-and-under moves to catch Zizic in the air.

But McCarty wants him to master the basics of verticality before learning how to control the paint from the ground, telling CelticsBlog that if he reaches as a rookie, he’s probably getting called for a foul.

“He’s figuring it out really fast,” McCarty said. “He’s really long. He does a great job of getting up and being able to go vertical on plays. He can move his feet. He just has to get more reps and I think if he does that, he’ll be fine.”

He is holding his own in most of these areas enough to contribute now, but the whole body of work is taking a lot out of him. Whether he is still fatigued from the late European schedule or simply adjusting to the league, he is confident he will catch up.

"I need just a little bit of time because this is my fifth game here," Zizic said. "So I'm doing my best -- actually, I expect a little bit more from myself. But like I said, I need just a little bit of time to (adjust) to this style of game."

McCarty wants his guy to just know when to pick his spots and always be thinking ahead.

“He's still trying get a feel for the tempo of the NBA game,” McCarty told CelticsBlog. “But he'll be fine.”