U.S. forward Landon Donovan missed his team's first training session on Tuesday ahead of a pair of crucial World Cup qualifiers, as medical staff evaluated his knee injury.
The U.S. play in Antigua and Barbuda on Friday and then host Guatemala in Kansas City on Tuesday as they seek a place in the final qualifying round from the CONCACAF region for the 2014 finals.
Donovan picked up the knee injury playing for his Major League Soccer team L.A. Galaxy against Real Salt Lake on Saturday.
A U.S. national team spokesman said there was no indication that Donovan's knee injury was worse than expected and staff were taking their first opportunity to have a look at the injury.
Just 11 players took the field on Tuesday for practice with other players doing gym work after travelling to Florida from their club action at the weekend.
F.C Dallas winger Brek Shea was also being looked at by medical staff after missing recent games with his club due to injury.
Juergen Klinsmann's team are currently level on seven points in Group A with Jamaica and Guatemala - just two teams will go through to the round of six next year which will produce three automatic qualifiers for the finals in Brazil.