Christian Pulisic was ruled out of Borussia Dortmund's Bundesliga clash at Hannover on Friday with a muscle injury:
Manager Lucien Favre brought in Marius Wolf in place of Pulisic for Dortmund's second league match of the new season.
The injury will be a worry to the United States ahead of the international break. Interim coach Dave Sarachan's side take on Brazil and Mexico in friendlies in September.
Pulisic's omission also means he missed the chance to make his 100th Bundesliga appearance for Borussia Dortmund since joining the club in 2015.
He picked up the injury during Dortmund's 4-1 win over RB Leipzig on Sunday. He is rated as doubtful for both international matches, according to ESPN FC's Stephan Uersfeld.
The 19-year-old was a real threat against Leipzig. He was also frequently fouled, according to Paul Carr at TruMedia Sports:
Pulisic was replaced after 77 minutes by Jadon Sancho. The substitute made an impact off the bench, as he set up Marco Reus for Dortmund's fourth and final goal.
The United States face Brazil at the MetLife Stadium in East Rutherford, New Jersey on September 8. They go on to play Mexico at Nashville's Nissan Stadium on September 12.
Sarachan had talked up Pulisic ahead of both games, per Mike Organ at The Tennessean.
"He's a game-changer," he said. "He's a guy that can make plays, create changes, score goals. That's a commodity you don't always get with teams. Of all the players now that I look at within our roster in terms of who can really change the outcome of a game, Christian is a guy that has that potential."
Sarachan may now have to make do without his star man for the two high-profile games which will be a blow as he tries to find the right blend between youth and experience ahead of the 2019 CONCACAF Gold Cup.