The 31-year old replaced Victor Valdes as a second-half substitute in the friendly game and has spoken of his happiness at the result, as well as the return to form of David Villa.
The game took place in Estadio Rommel Fernandez Gutierrez in Central America, and it was a comfortable victory for the 2010 World Cup winner, with Pedro, David Villa, Sergio Ramos and Markel Susaeta getting among the goals.
Although Panama is rated 46th in the FIFA world rankings, some 45 places below the Spaniards, Casillas was pleased with the display from his teammates.
"It was great," he told reporters. "The Panamanians celebrated their goal like they had won the World Cup, they really are wonderful people."
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