Only four players from the U.S. World Cup team return: midfielders DaMarcus Beasley and Pablo Mastroeni and strikers Landon Donovan and Clint Mathis.
All 10 MLS teams are represented on the 23-player training camp roster. The Columbus Crew and New England Revolution will have four players each in camp.
Returning is D.C. United midfielder Ben Olsen, who has missed nearly two years after suffering a series of ankle injuries.
The average of the U.S. team is only 24. Kansas City's Chris Klein is at 26 the oldest player picked.
''The challenge of building a team capable of qualifying for the World Cup begins again,'' said Arena. ''There are a lot of talented young players with great potential in MLS, and over the next two years we plan to provide them with quality international experience in order to evaluate who can compete at the international level.''
U.S. TRAINING CAMP ROSTER:
Goalkeepers: Adin Brown (New England Revolution, 0 caps/0 goals), Tim Howard (MetroStars, 1/0), Nick Rimando (D.C. United, 0/0).
Defenders: Wade Barrett (San Jose Earthquakes, 0/0), Carlos Bocanegra (Chicago Fire, 6/0), Dan Califf (Los Angeles Galaxy, 1/0), Brian Dunseth (Columbus Crew, 0/0), Chad McCarty (Columbus Crew, 0/0), Eddie Robinson (San Jose Earthquakes, 0/0), Ryan Suarez (Dallas Burn, 0/0).
Midfielders: DaMarcus Beasley (Chicago Fire, 15/3), Leo Cullen (New England Revolution, 2/0), Daniel Hernandez (New England Revolution, 0/0), Chris Klein (Kansas City Wizards, 6/0), Kyle Martino (Columbus Crew, 0/0), Pablo Mastroeni (Colorado Rapids, 13/0), Ben Olsen (D.C. United), Eric Quill (Kansas City Wizards, 0/0), Sasha Victorine (Los Angeles Galaxy, 1/0).
Forwards: Jeff Cunningham (Columbus Crew, 4/0), Landon Donovan (San Jose Earthquakes, 28/7), Clint Mathis (MetroStars, 25/10), Taylor Twellman (New England Revolution, 0/0).