Jozy Altidore strained his left hamstring in the 23rd minute of the United States' 2-1 win over Ghana on Monday.
Altidore will be reevaluated on Tuesday.
"It was a little bit of a shock that Jozy got injured," Jurgen Klinsmann said. "It was a tough pill to swallow."
Altidore was taken off on a stretch and replaced by Aron Johannsson.
"My heart goes out to him because he's been working hard," said captain Clint Dempsey. "He's been looking sharp. You know how much he wanted to do well. ... You could see the tears in his eyes going back to the locker room. We wish him a speedy recovery. He's a big player for us. It hurts to have him go out of the game today but other players have to step up now."