U.S. forward Jozy Altidore will miss Sunday's World Cup game against Portugal because of his strained left hamstring.
Altidore was hurt during the first half of Monday's win over Ghana.
U.S. team spokesman Michael Kammarman said Thursday the Americans were hopeful Altidore can return at some point during the tournament. The Americans complete the first round against three-time champion Germany on June 26.
Defender Matt Besler, who came out of the Ghana match at halftime because of a sore right hamstring, should be available for Sunday's game in Manaus, Kammarman said.
Aron Johannsson replaced Altidore for the second half against Ghana. Chris Wondolowski is the other striker in the squad who could join Clint Dempsey in the attack.
Dempsey has not decided whether he will wear a mask to protect his nose, which was broken during the Ghana game.