Costa Rica coach Alexandre Guimaraes has named his squad for the warm-up friendlies against the World Cup host nations.
The central American side travel to the Far East for games against Japan on 17 April and South Korea three days later.
However, Guimaraes' planning has been hit by injuries to key players and a general lack of preparation.
"There are players who are seriously injured and we don't know if they will be ready for the World Cup," he said.
"Also, the time to prepare is very short."
The three major injury concerns are Paulo Wanchope, the striker who has just helped Manchester City to promotion to the English Premiership, plus defender Jervis Drummond and skipper Reynaldo Parks.
Defender Gilberto Martinez is named in the squad but may also miss the trip through injury.
Guimaraes, who played in Costa Rica's only previous appearance at the finals in Italy in 1990, has had to deal with a row between clubs and the national football federation over the length of the domestic season.
Costa Rica have been drawn in Group C for the finals along with former champions Brazil, Turkey and China.
China will be well-versed in the Costa Ricans' style as Bora Milutinovic was their coach at the 1990 finals, while Guimares believes that Turkey and Brazil will be formidable opponents.
"The Turks are a very strong team and have a strong spirit," he said.
"And Brazil will be one of the favourites."