Costa Rica coach Alexandre Guimaraes told the national press that his side urgently needs to correct mistakes that will cost them dear at the World Cup.
He was speaking after Costa Rica lost 2-1 at home to Colombia on Thursday in their final friendly before heading to Japan at the weekend.
"The defeat is a good lesson, we have to work to avoid these mistakes in the future, they can't happen in a World Cup," Guimaraes told reporters.
He referred to Colombia's second goal, when a defensive error left striker Rafael Castillo with the goal at his mercy.
The Costa Rican press were unhappy with the result but could only hope it would help focus the team.
"The farewell as an excuse," was the headline in El Heraldo, which wondered whether Guimaraes' recovering players could be fit on time.
"A goodbye without smiles," La Nacion said, concluding that the game had at least been "a good trial".