USA striker Jozy Altidore will have an MRI scan on his hamstring to ascertain the extent of the injury.
The Villarreal man was subbed out in the ninth minute of the US national team's 2-0 CONCACAF Gold Cup quarter-final win over Jamaica on Sunday and will undergo a scan today ahead of Wednesday's semi-final.
Altidore, who has scored two goals so far in the tournament, is a chance of missing the final four clash with Panama but Bob Bradley said a decision would be made once they know more about his problem and was confident that any potential replacement would do the job.
"We will have an update on Jozy later. He's played well thus far in this tournament and hopefully he'll still be available for us,'' said Bradley.
"We've had different guys come through for us so far. Everybody is needed in this kind of tournament.
"This is a tough tournament in terms of the games and how fast they come and the travel. We keep talking to the players that aren't getting minutes and making sure that we are still training these guys and pushing them hard because they are all going to need to be ready."