After beating Australia by ten points Wednesday night, the U.S. men’s basketball team appeared to be done with the drama at the Olympics. But Friday against Serbia things got even worse for the two-time defending Olympic champions, as their struggles on both ends of the floor nearly cost them the game.

The Americans hung on to win 94-91, with a Bogdan Bogdanovic three-pointer in the final seconds missing the mark. Kyrie Irving led six Americans in double figures with 15 points, but that offensive balance masks the fact that once again that their ball and player movement wasn’t at the level that they needed it to reach. Far too often the U.S. fell into the trap of “iso ball,” with one player monopolizing the basketball and the other four simply standing around hoping that something would happen.

WATCH: USA men’s basketball outlasts Serbia

Given their individual talents the U.S. can get away with this against most teams, but after being pushed by Australia the Americans met an even tougher challenge in the form of Serbia. That will have to change as Mike Krzyzewski’s team moves into bracket play, where a loss would have far more damaging consequences (no gold medal) than in group play.

Defensively, once again defending ball screens was a problem as Serbian point guard Milos Teodosic was able to create quality looks for both himself and other players. But the ball screen was just one aspect of Serbia’s offense that gave the U.S. fits, as they were committed to moving the ball and using solid player movement to make the Americans chase the ball on many occasions. Teodosic finished with 18 points and six assists, and forwards Nikola Jokic (25 points, six rebounds, three assists) and Miroslav Raduljica (18 points) were the beneficiaries of Serbia’s offensive execution.

Serbia coach Aleksandar Djordjevic: "San Antonio's game in last decade showed us how the game should be played.” — Jeff Zillgitt (@JeffZillgitt) August 13, 2016

Jokic, who was one of the best rookies in the NBA last season with the Denver Nuggets, shot 11-for-16 from the field and was able to make shots both inside the paint and out throughout the evening. Even with their familiarity with his skill set, Jokic gave the American big men fits regardless of the lineup (conventional or small) that Krzyzewski put on the court.

Even with the issues on both ends of the floor the United States is still undefeated in group play. But these last two games should serve as a wake-up call for them, especially the ten players who are playing in their first Olympics. Next up for the U.S., which has clinched the top spot in Group A, is a matchup with a France squad led by San Antonio Spurs point guard Tony Parker Sunday afternoon.