SHANGHAI — The U.S. finally got to enjoy an easy night at the World Cup.

There might not be many more of those.

Jaylen Brown scored 20 points, Kemba Walker added 15 and the U.S. rolled past Japan 98-45 Thursday in the Group E finale. And now, the stakes get higher with the Americans set to face Greece — and NBA MVP Giannis Antetokounmpo — in a second-round opener on Saturday in Shenzhen, China.

"They were very serious tonight and they respected the Japanese team very much," U.S. coach Gregg Popovich said. "They didn't take anything for granted and they played hard. So I was pleased with their performance."

Harrison Barnes scored 14 points while Joe Harris and Donovan Mitchell each had 10 for the Americans (3-0), who are bidding for an unprecedented third consecutive World Cup title. The 45 points allowed were the fewest yielded by any team in the first round of this World Cup, the 53-point margin was the third-biggest so far in the tournament and Mitchell thought it was the best defense the Americans have played this summer.

"From the jump, I think for the full 40 minutes," Mitchell said. "We've had games where we played 30 minutes of great defense or 35 and kind of let up a little bit. I think for a whole game, to really lock in and set a tone, it was really impressive."

Yudai Baba scored 18 for Japan (0-3), which will play in classification games the rest of the way. Rui Hachimura, Japan's best player and the No. 9 draft pick this year by the Washington Wizards, was held to four points on 2 for 8 shooting.

"I've got no excuse," said Japan guard Yuta Watanabe, who scored nine points. "This is the way we are right now."

A U.S. program that is accustomed to blowout wins, particularly when it has NBA players, hadn't enjoyed one yet in six games against international competition this summer. The biggest victory margin before Thursday was 21 in the World Cup opener against the Czech Republic, and the U.S. came into the group finale with a plus-59 scoring differential in four exhibitions and two World Cup games.

This one, two days after the Americans needed late-game heroics to beat Turkey 93-92 in overtime, was drama-free.

It was 13-0 before Japan scored, 23-9 after a quarter, 56-23 at halftime and 73-25 midway through the third quarter when Hachimura got loose for a dunk and his first points of the night. Somehow, matters could have been even worse for Japan: The U.S. missed seven of eight shots during one first-quarter stretch and finished shooting 48% for the game.

"I think we've got a lot of room for improvement," Brown said.