Boston Celtics guard Kemba Walker missed Team USA's practice ahead of their FIBA World Cup game against Brazil, though he remains probable to play.

According to Brian Windhorst of ESPN, Walker is dealing with an unidentified illness that forced him to sit out their recent practice session. Meanwhile, Jayson Tatum is progressing but remains out due to the ankle injury he sustained during their showdown against Turkey in the first round group stage.

Walker has been one of the best players for the American side. He's averaging 14.3 points, 3.3 rebounds and 6.3 assists through the first four games of the tournament. He's one of the main reasons why Team USA remains undefeated, so missing him will certainly be a huge blow to a team aiming to keep their perfect record intact.

There have been a lot of doubts about Team USA's ability to win the FIBA World Cup title, especially after some of the NBA's top players withdrew and declined the invitation to represent the country. Still, the Americans were able to exceed expectations, and it seems they are peaking at the right moment.

Should they win against Brazil, they will be moving on to the next round of the tournament because they will finish with the best record in their group. But even if Team USA loses, a Czech Republic loss at the hands of Greece could still propel them to the quarterfinals — where the knockout stage of the FIBA World Championships begins.