Bolton midfielder Stuart Holden faces at least the next six weeks on the sidelines after fracturing his right fibula.
Holden, who joined Wanderers in January on a short-term deal until the end of the season, sustained the injury during USA's 2-1 friendly defeat to Netherlands on Wednesday night.
Holden had started Bolton's last two matches, impressing manager Owen Coyle, who also confirmed the 22-year-old's contract has been extended through to the end of next season.
"It's disappointing for Stuart because he has come into the team and done ever so well," Coyle said. "What we do know is he will come back bigger and stronger, but it is sad for him to miss out at this moment in time.
"He's come in with a real hunger and desire to do well for our club, and in the two games he's played, we've seen his quality."
Coyle is hopeful the injury will not damage Holden's prospects of playing in the World Cup, with the United States' opening group game against England on June 12.
"Only time will tell," he said. "We're erring on the side of six weeks, and if that is the case then he will be capable of playing the last part of the season for us and putting himself in the frame for the World Cup."
With regard to Holden's extended deal, Coyle feels he has already proven himself in the short space of time he has been with Bolton.
"We've already spoken with him and his representative to assure him he will be here for longer because of the belief I have in him, and the quality he has shown since he came to the club.
"When we signed him, within the contract there was the option there to extend it further, which we will do. It augurs well for his future and that of the football club."