USA started their 2014 FIFA World Cup campaign on a bright note, but they will have to make major adjustments in their upcoming matches as reports indicated that Jozy Altidore will be out for the rest of the group stages.

The U.S. Soccer Federation announced on Thursday night the Altidore will not play against Portugal on Sunday after hurting his hamstring during their 2-1 win against Ghana on Monday.

USSF spokesman Michael Kammarman said that their star striker is undergoing treatment in hopes of returning quickly from the hamstring injury, but reports indicated that Altidore might also miss United States' final group game against Germany.

U.S. midfielder Jermaine Jones admitted that losing Altidore is a big blow to their campaign, but he is optimistic that the team will manage to overcome the adversity and clinch a spot in the knockout stages.

"It's bad news, but the team will handle it," Jones said via The Washington Post. "I don't know how [Klinsmann] will play and what formation he will play. But everybody is ready and wants to make the next step."

Without Altidore, Klinsmann is expected to pin his hopes on Aron Johannsson, who came in as replacement in their tournament opener, or Chris Wondolowski.

Jones said that both players can make an impact in their upcoming games against Portugal and Germany.

"Wondo is more a finisher in the box," Jones said via USA Today. "Aron is more the guy who's good with ball and does one against one better."

Johannsson is coming off an impressive season with Dutch club AZ Alkmaar wherein he netted 26 goals, while Wondolowski finished as one of the top goal scorers in the Major League Soccer.

But when it comes to experience, Johannsson has proved that he can hold his own against the international heavyweights, which makes him as the most likely replacement to Altidore against Portugal.

Aside from Altidore, Matt Besler was also considered as doubtful for Saturday's match, but Washington Post reported that the central defender will play after recovering from tightness in his right hamstring.

Team captain Clint Dempsey, who sustained a broken nose in their opener, will also play against Portugal, but will likely wear a protective mask for the entire tournament.