Milwaukee Bucks head coach Doc Rivers cited a lack of rest after their NBA Cup triumph as pivotal in their defeat to the Cleveland Cavaliers on Friday.

Donovan Mitchell starred for the Cavs as they improved to 15-1 at home, with his 27 points helping his side to a 124-101 victory against the sluggish Bucks.

Giannis Antetokounmpo had 33 points and 14 rebounds for the Bucks, but they struggled without All-Star guard Damian Lillard after he was ruled out with a strained calf.

But Rivers, who watched his team fall to 14-12 this season, suggested his side were suffering a hangover following their win in Las Vegas a few days earlier.

"I said before the Cup started that the Cup had meaning, you could see that, you could feel that. All four teams there they wanted to win, and they played that way," Rivers said.

"But what they need to do is the time after the Cup. Oklahoma played last night. I can’t imagine it and they won. At least they had enough energy to do that.

"During the Cup, the teams that aren’t there are getting a lot of rest.

"And then we played a cup and now, bam, we are back in it. I think they have to figure out the back end of it, and I think they will."

The Cavaliers, meanwhile, improved to 24-4, their best start to a season since 2008-09 when LeBron James and company finished 66-16.

They were also boosted by the return of forward Max Strus, who missed the first 27 games of the season with an ankle injury.

Strus finished the game with nine points in 19 minutes, hitting three of his eight 3-point attempts while also dishing out two assists.

And Cavs head coach Kenny Atkinson is confident that Strus' return to the squad can help energise their offence moving forward.

"I mean the energy, that injection of energy we talked about, he's going to come in and everything that goes with that, it's like turbo," Atkinson said.

"He's on turbo between the cuts and flying off staggers.

"You saw it last year. What were we, 4-6, without him or something like that? [It's helpful] just for defenses to have to pay attention to him.

"That's the biggest thing about our offence. You really have to make so many decisions, and now you add another guy who shoots it at a high clip, that's ultimately what makes him special, as well as being able to be a great rebounder, hustle plays, little things, but having him back, being able to have another weapon is huge."