FC Dallas midfielder Kellyn Acosta and defender Matt Hedges have been dropped from the U.S. national team training camp because of injuries, while Vancouver midfielder Kekuta Manneh has left to join the Whitecaps for preseason training.
Acosta has a mild left ankle sprain, and Hedges has a mild right knee sprain, the U.S. Soccer Federation said on Monday.
U.S. Soccer announced last week that Manneh has been granted citizenship, but he still must receive a waiver from FIFA to play for the U.S. team, since he was previously called in for the Gambia's under-20 team.
They will not be replaced on the squad before the Americans play Serbia on Sunday in San Diego, in their first game since Bruce Arena replaced Jurgen Klinsmann as coach in November following losses to Mexico and Costa Rica in World Cup qualifiers.
The U.S. also plays Jamaica on Feb. 3 at Chattanooga, Tennessee.
Twenty-eight players remain on the revised roster:
Goalkeepers: David Bingham (San Jose Earthquakes), Nick Rimando (Real Salt Lake), Luis Robles (New York Red Bulls), Brian Rowe (LA Galaxy)
Defenders: DaMarcus Beasley (unattached), Steve Birnbaum (D.C. United), Brad Evans (Seattle Sounders), Greg Garza (Atlanta United), Taylor Kemp (D.C. United), Chad Marshall (Seattle Sounders), Keegan Rosenberry (Philadelphia Union), Walker Zimmerman (FC Dallas), Graham Zusi (Sporting Kansas City)
Midfielders: Alejandro Bedoya (Philadelphia Union), Michael Bradley (Toronto FC), Benny Feilhaber (Sporting Kansas City), Jermaine Jones (LA Galaxy), Sacha Kljestan (New York Red Bulls), Sebastian Lletget (LA Galaxy), Dax McCarty (Chicago Fire), Darlington Nagbe (Portland Timbers), Chris Pontius (Philadelphia Union), Wil Trapp (Columbus Crew SC)
Forwards: Juan Agudelo (New England Revolution), Jozy Altidore (Toronto FC), Jordan Morris (Seattle Sounders), Chris Wondolowski (San Jose Earthquakes), Gyasi Zardes (LA Galaxy)