The former City pair signed for Barca last week with their contracts running down.
Guardiola told Mundo Deportivo: "They are great signings, they are both a total success.
"El Kun has already proven in his career his scoring and is a very good kid and Eric is a spectacular signing, and I told Ronald (Koeman).
"He is a jewel as a kid, very intelligent, eager to learn, he absorbs everything.
"With time he will be one of the Barça captains of the next decade, you will see it."
Of his own future, Guardiola added: "I have two years of contract and I am delighted in Manchester and so we will continue."
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